I think there are two primary reasons.
1.) A developer wants to develop/test against an x.y release that only changes minimally (major bug and security fixes) for an extended period of time.
2.) The point release model where you can decide when/if to install upgrades is just "how we've always done things" and a lot of people just aren't comfortable with changing that (even if they effectively already have with any software in public clouds or SaaS).
I largely agree with your other points.