Absolutely agreed, this always bothered me. I always felt like I was being punished and made to work the tougher harder shifts because other folks had chosen to have kids.
Folks should not be punished for not having kids, if someone has kids that's their problem.
Find a job somewhere else then. Where I work, I don't see any differences between the time parents take off and non-parents. We're split about 50-50 breeders and non-breeders. In my wife's office, there are legit parent abusers of the time off system but then there are also non-parents who abuse the same time off system, and both come down to the boss there being a lot more wishy-washy about it than my boss.