I have a Google account I use for analytics, webmaster tools, etc... and Google is always prompting me to turn Google+ on as well. It wasn't automatic with my account. I had the account before Google+ existed though so maybe it is just automatic with new signups?
That's lame. People should only have a Google+ account if they actually want it. I personally find this behavior distasteful and Google is obviously using it to artificially inflate their numbers.
Why would Google want to fragment its userbase by having to separate classes of accounts, Google+ accounts and regular ol' Google accounts. That would be lamer.
I made a new Gmail account for my mom a few days, now she has a Google+ account too but I doubt she'll ever touch it.