One day, Google Plus's suggestions for "friends" I should add to circles included 2 people I'd already circled, 2 versions of another person, and even another version of myself!
So, yes, multi-account Google stuff is painful. I don't know why they don't see that and fix it.
I used to wish for better integration between Google's various products. Now we have what we have, and I don't use Google anymore. Ironically, G+ was the service I was most excited about from any vendor in recent memory, and their management of that was what finally pushed me out of the nest. At this point they're only a backup account, like Yahoo used to be before they dropped me for inactivity.
So yeah, Google could decide to integrate your multiple accounts, but I expect their implementation of that to piss off a lot of people.
So, yes, multi-account Google stuff is painful. I don't know why they don't see that and fix it.