Major reason is, to attempt to stop boosting. Cod Research found that, alot of people boost for perks,and emblems/Titles. Which is why, Treyarch made it where you can custom make your emblem, due to it going out of control, banns are being hammered. Anyways, Perk boosting is the biggest out of the Boosting. While, from Ghost pro in Blops 1, had more of a Shoot down K.S, you had others that required kills, while stunned, or while doing somthing. Very hard things. I'm kinda glad to be honest, you don't see as many boosters.
The amount of perks is fine.
Problem is, only hardline, scavenger, ghost, engineer, lightweight, marathon, toughness and dexterity are useful.
Flak Jacket, cold-blooded, blind-eye and fast hands are ineffective.
Hardwired, awareness, dead silence and tactical mask are nearly useless.
Cold-blooded is kind of effective if the enemy use the largest killstreaks, but only then.
In my humble opinion, pro perks were annoying.
I'd rather have perk challenges that give me loads of experience, and not improve the perk, so that I can level up and prestige faster.