Convenience and sense of freedom. No license required, can lend it to friends or kids. Can be parked anywhere. Can be loaded on a car, ferry and some places even the metro. Can ride them on bike lanes, the forest and the sidewalk. More approachable diy maintenance. Don't need full leather protection, just a helmet and t-shirt and you are good to go. If you are only traveling max 30km within the town, you don't need anything faster.
Some bicyclists in Palo Alto do, probably because they can't take their Ferrari's with them. A former business partner had a ~$8k bicycle stolen from Castro St. downtown in a very public area. All it takes to steal is 30 seconds and a battery-powered angle grinder. If someone doesn't have Tile, AirTag, and a GPS tracker on such a bike, then they're an idiot.
Hahaha. I hope a precondition to any bicycle theft includes requires 1 or more tracking devices and not transiting anywhere near a major metropolitan area or any city area with a drug problem.
Bigger isn't always better.