Thats why I said "generally". There are certainly people for whom bikes are utilitarian. I just suspect that of every 100 ebikes/normal bikes sold in the US, 99 go to people who ride mainly for fun and recreation (with some utility thrown in here and there). I bike commuted pretty regularly from 2005 through 2017 (and only stopped because I started working remote) and I wouldn't even say that it was utilitarian for me. I had a car and did drive sometimes, commuting on the bike was just more fun and kept me in shape for longer rides on weekends.
If we're explaining why $10,000 bikes exist, its because most people buy bikes for enjoyment, and what people are willing to spend for enjoyment does extend into the 10s of thousands frequently enough for those to be worth selling.
This discussion reminds me of guitars. If you are one...or if you know a 'guitar person'...you know that buying guitars can be addictive. Of course we can only play one at a time and of course there are plenty of $99 guitars out there....but many 'guitar people' own 10's of guitars which cost thousands (or 10's of thousands) each. Additionally....guitars require care and maintenance!....they are like pets!
Humans have consistently justified behaviors throughout the ages and I am not immune. My Cervelo buddy who likely rides about 25 mile per week but owns 4 bikes each of which cost more than BOTH of my ebikes put together?.....that's his business. Surely there are plenty of people that feel that my two Spesh Vados purchased for total $5250 is insane....but to me it was a bargain.
So long as my purchasing decisions are not a burden upon my fellow inhabitants of earth I say 'mind your own business' lol. My/your purchasing decisions don't need to make fiscal sense to others.