often theyre miners. Especially early miners (from when the POW reward was higher).

if you look them up on steemd, youll almost almost always find a lot of XXX found a pow on t heir account. for example ashliegh or any of the badgers...

Incidentally, it looks like "michael-a" and michael B were created by the steemit account, and got all their vests from there... this makes it look some kind of accounting thing.