Well, I feel the very same way. I really don't know if there is any benefit from this. Actually it's just annoying to login and log out when doing different tasks. I'm sure they're able to link all of those accounts together very easily.

One limitation I know of is google can not change country of residence for merchant accounts, so make sense to keep different accounts atleast where it associated with card/bank.

I don't get it. What's wrong with profiling?