Well, no kids here yet, but I was one of the few of my friends who didn't have one. I didn't really know why at the time, but it was because I had proved to my mother that I could be counted on to be reliable and do the right thing. I always tried to let her know when I thought I'd be back and I called her if that looked like it would change.
Don't get me wrong, I was no goody-two-shoes. I went clubbing and to concerts in Washington DC, as well as parties, etc. I suspect if I had seriously violated her trust at any point, she would have established a curfew for me. I had freedom and trust from my mother while all my friends lied and deceived their parents in order to do what I was doing with Mom's knowledge.
Occasionally Mom did request that I be home for by a certain time and she certainly didn't allow me to do everything I wanted to do, but curfews per se never entered the equasion.