Many of them do come from a disregard for privacy. That bothers me, but some people are happy to make that trade-off for better services.
I would suggest that MOST people are happy to make that trade off. At least until your personal information is hacked and taken from googles servers.
To be fair, practically speaking, it's more likely that your "personal information" will be hacked if it is in your possession vs. when in Google's cloud.
In my case, it's not that I don't trust Google's cloud security. It's the unknown third parties they sell my info to's security that bothers me.
Which the market, and consumers’s revealed preference, has demonstrated doesn’t matter one whit.