HTupolev

1-While weight does matter, you get proportionally less improvement for weight savings on a touring bike versus a racing bike. If you had a magic racing bike that weighed zero pounds, it would feel pretty crazy to ride; if you had a magic touring bike that weighed zero pounds but was carrying 30 pounds in back and 20 pounds up front, it would still handle more or less like a loaded touring bike. So the appeal in spending thousands of dollars to shave off a couple pounds is less.

2-A lot of the cost of high-end racing components is for aero designs; box-section rims are a lot cheaper to make than sophisticated fairings! While aerodynamics always matters, at lower speeds it's a proportionally smaller factor in total drag on the bike. Since touring is usually a much lower-speed activity than racing, touring bikes get smaller benefits than racers do from aero gear. So the appeal in such improvements is less.

3-The more expensive something is, the harder it is for people to stomach beating the crap out of it. Touring bikes are more difficult to pamper than racing bikes: you usually don't have your full array of quality cleaning tools and such when you're touring, and it's far less convenient to choose to do things like only ride in dry weather.

4-Market size. It's easier to profit in an ultra-high-end market when, after R&D and manufacturing setup costs, you expect to sell 200 ultra-high-end units and not 4.

5-Replacement part availability and compatibility. If a road racing bike breaks down and you can't find a quick repair, you'll have to either cancel the ride that day or hop on a different bike. If your touring bike breaks down and you can't find a quick repair, your tour is halted. There's more at stake!
Compatibility is a lot better in lower-end, simpler, (and vintage) parts. If I've got friction shifters and a 7-speed cassette, and I drop my bike on my rear derailleur and bust it up, any cheap MTB derailleur would work perfectly as a drop-in replacement. If you drop your bike on a Di2 derailleur, you'll have to find another Di2 derailleur to get that functionality back (or replace your entire drivetrain with whatever's available).
I recently built up a bike with a 7/8-speed Acera rear derailleur, old unlabeled front derailleur supposedly ordered by Bridgestone through SunTour or something, SunTour barcons, 6-speed SunRace freewheel, vintage Sakae triple crankset, and a SRAM 8-speed chain. Aside from limit screws, the whole drivetrain worked perfectly first try with no adjustment.

Even with front and rear loads of tens of pounds, it's possible to design a bike's geometry to handle this stably, and even heavy (rigid) touring forks are usually on the order of like 2 pounds. Heavy frameset is not something that inevitably causes poor handling.