Okay ... if you are a businessperson, you know better.
There is the ultra-high-end/luxury market, where the more ridiculous the price, the better----a $500 watch will sell better at $50,000 than $5,000 to certain customers, which is why people pay tens of thousands of dollars for a watch which is less accurate than the clock in their phones. Beyond a certain point, the ridiculous price ensures exclusivity ... not just anyone could afford to overpay this much for a simple timepiece.
There are also Very expensive watches (and other objects) which are not Ultra-high-end but are still very expensive ... the $5K to $25 K range, say ... A(enough watch experts here to fill in the blanks) that bring their wearers a very certain and serious satisfaction but Not simply because they are expensive .... well there are some trashy folk whop buy $10 K Rolexes ebcause they think that means something (and it does, but not what they think) and there are people who buy $10K or $20 K Phillipe Pateks because they have the cash but really like the watches, the feel and looks, the workmanship .... timepiece aficionados with big budgets.
With bikes ... there are people who pay a lot of money either because they can (remember that TrekMogul guy?) or because they want to buy the same bikes the pros ride ... orb better .... but most of them are riding them competitively (though not at the pro level.)
I personally conversed with a guy with an $18,000 bike (and this was a few years ago) because we both rode the same deserted bit of road which turned out to be private and watched by private security. He was a racer but he was a weekend racer who might have won a few Cat 3 and cat 4 races, riding in Pro 1-2-3 and being part of the peloton. He was enough into rising that he wanted the best bike for racing he could buy .... just as if he was going to race in a box-stock road-racing series, why not buy the fastest car he could? He spent all his discretionary income on bike stuff. His choice, his passion, his option.
There is Zero "performance" gain for a 3x system if you equate performance with speed or racing. Zero. Racers don't haul weight, and the gearing available with any 11- or 12-speed 2x system is low enough for any hill an unladen rider might want to ride .... or the rider will fail, but at the regional/state level, sometimes that happens. (It happens on the Pro Tour too, but usually only after injury or due to illness.) Otherwise, the people who design race courses consider the ability of the riders when deciding which climbs they include, just as they decide on the length of the race (usually two-thirds or less than a Grand Tour stage .... last road race I attended the pros did 68 miles, and the last crit, the pros raced 70 minutes.) Riders can get through with a 53-39x11-28 or 11-34 or whatever ... or use a 50-34 if the course has a lot of hills.
There is no gain to be had from the wider range of gears on a 3x, and the 3x weighs more.
HOWEVER ..... most riders Do Not Race. Most riders don't train three to five days a week, or ride 200 miles per week. And for those riders, at least the ones living in hilly terrain, a 3x DOES offer better "performance" in that it lets them work in a more favorable cadence range and still get up the hills, even when carrying groceries, camping gear, or just lots of water for a long ride where there won't be any safe water stops.
As I said above .... Most of those riders can get by with a wide-range 2x system, but that does not mean it is as good. The gaps between gears and the compromise at one end or the other (either they spin out on the downhills and pedal too fast on the flats, or are really struggling on the steep hills) is Bad Performance ... but for most riders, sourcing a 3x system is too much work. They basically decide to eat what the manufacturers feed them .... much as do many who would prefer rim brakes, or hated press-don't-fit bottom brackets.
I have a sweet 50-40-30 10-speed crank on the shelf, waiting for the right bike .... most people cannot be bothered to source and buy and store such stuff. Then again, I replaced all my press-don't-fit BBs with Wheels MFG threaded BBs... which most don't do.
Nobody is a "Super-Pro Tourer" who wants to build a $40,000 bike to drag gear around the world. There simply is no "Luxury/High-End" Touring market. There is no high-end touring market. People who buy touring bikes are planning to bash the snot out of them (gently) by loading them with as much gear as they need or can carry, and then riding them more miles in a year than most racers .... leaning them on trees or guardrails or on the ground, cleaning them very infrequently ... most tourers spend as much on their bags and other gear as on the bike, because a bike can be had almost anywhere but if you rip a bag and cannot so it ... Most tourers prefer steel and anything bullet-proof ....
All that aside (and here is the info that keeps getting ignored in these threads):
https://www.performancebike.com/shim...=1468&lg=fk191
There is a Ton of high-quality 3x gear out there. it just doesn't come standard on many bikes. Shimano (and I assume other manufacturers) Do offer really good 3x drive train parts. I don't know where the myth that 3x is gone, came from.
True, most bikes are not specced 3x and most bike-buyers are not interested in dropping several hundred dollars on drive train upgrades on a new bike .... Would we see more 3x on the road if more bikes were offere3d with 3x? Hard to say, because a lot of cyclists buy into the whole "cyclist" look, and try to look like racers .... and a lot of those that don't were rising 3x citi-bikes and cruisers which are no offered only in 1x because the riders didn't really bother shifting to get max performance anyway.
So ... yes there is a market and the major manufacturers service it. No, they do not advertise that they offer such stuff because it is probably cheaper and easier to offer fewer models with fewer parts (economies of scale ... produce a lot more of the same thing for less, or have to change production parameters more frequently to produce smaller runs of more different parts ... . simpler is cheaper, bigger is cheaper. So, the availability of 3x, and the potential benefits to many riders, is not advertised. The people who want it, will seek it out and pay the premium.
There Is a "lucrative" 3x market ... and it could be bigger, but it would cut into profits generated by teh 2x market, so ....
That's how I see it.
By the way ... it is quite possible that Shimano with its newly revamped drive train lines, will make MTB 3x totally compatible with road parts ... we shall see.