It has a lot to do with the way the update now appears in System Preferences. Feels optional. Also, many people are a little nervous about fresh releases due to some of the bugs we’ve seen in past updates. I’m waiting for 15.0.1. Normally I’d be a day one upgrader.
It’ll be due to the new square edge design. The current watch band connectors are designed for curved edges. I mean they’ve used the same bands for a few years now - 6 in fact which is like 30 in tech years. Can’t be expected to never change.