Not actually a silly question. Most of us have probably asked ourselves the same thing, especially every time we bring a new one home.

Everyone's got a different reason (and the numbers 10-20 are certainly arbitrary) but for me, it just sort of crept up on me. Obviously you need a bike for each type of riding you want to do, but as someone else pointed out, even bikes in the same "category" can be dramatically different. It's fun to ride different bikes and experience the different personalities and characteristics of each. And if you've built or restored them yourself, you sort of become attached.

I've often thought about selling one bike or another, when I'm looking at them all in the garage and realize that I have a lot of redundancy. But then I take the bike out on the road and think "Man, I can't sell this." Plus it gives you flexibility. I bought an indoor trainer and didn't have to worry about having a bike to put on it. I chose the Rockhopper and still have two other MTBs that serve me well as gravel bikes. Also when guests come and visit, between my wife and I we have bicycles for everyone.

I think space is probably the limiting factor for most people. But if you have the room, there's little reason to get rid of a bike that you love just because you got a new one.

No matter the number, if someone has bicycles that they display but don't ever ride, that's a collector. You're choosing bikes for a different reason than their ride characteristics. Right now I'm trying to resist the temptation to buy a 1973 Schwinn World Voyageur in Sunset Orange, just because it's so pretty. I'm sure that I'd ride it a few times just for fun and nostalgia, but it's never going to be the bike I choose to ride over some of my others on a normal basis. I would find a place to put it on display, and now I'm a collector.

If you a have large number of bikes that are neither ridden nor being displayed as a collectible, that's a hoarder.