Cost savings is why federal does it.
I find it annoying. I seperate them out and at some point when i get enough from range pickups ill either run a batch or trade em off for other brass.
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." — L. Neil Smith