- Google’s large enough
- No one (or at least no one with enough clout) has taken Google to the mat for updating its web apps and being too lazy to document changes
- Google offers absolutely no customer service channels so people can’t actually bother it when (not if) real world problems arise
Period.
These are some of the reasons why I use as few Google services as possible; it’s just not worth the hassle. I would never rely on a service for anything important, that doesn’t offer any kind of customer support.
If I didn’t need Google Reader, I’d delete my Google ID in a heartbeat.