I think 2013 was the first year of the rookie wage scale. So it's been in place about 7 years now.
I always hear the argument about teams being able to cut players and that contracts should be fully guaranteed. But players can have them fully guaranteed. They can negotiate for it. Most do in fact have a portion of their contract guaranteed. And frankly I think the ability to cut a player and keep some of that money helps to keep a player motivated. If they are going to make the money regardless, what is their motivation to show up and work their ass off? Clearly winning football games isn't enough motivation for some guys.
Like I said, no one is returning their signing bonus because their play goes to shit. So why should a guy not even close to free agency be bitching that the 8 mil he will count against the cap isn't enough.