I know I'd certainly not turned out as well without it when I was raised. THAT was about the only thing that would get my attention. I wasn't a bad kid...but, mischievous. I didn't get that many spankings, but, the ones I got I deserved, and it certainly modified my behavior in a permanent fashion.
Do you really know you wouldn't have turned out well, though? I mean, maybe you're right, but I've noticed that most people are generally inclined to justify however they were brought up, whether it was with or without spanking. I wasn't spanked (except by one boyfriend my mom had when I was young, who spanked my brother and I maybe 2 or 3 times--I don't remember him fondly, not surprisingly) and I feel like I turned out well. I also feel like I would probably be more resentful and less compassionate toward other people if I was spanked.
But I can't say for sure; it's an educated guess. And I don't think you know for sure that your parents couldn't have come up with a set of privileges that you would have been motivated to earn and keep with "good" behavior.
One thing I do know is that I've seen even kids who were badly abused or molested justify what their parents did, and they will often say "I deserved it". So it doesn't surprise me to see someone justify being spanked a few times, even though the research suggests it's not the healthiest approach.
I guess if I were a kid today....rather than strike my behavior up to just 'being a boy'....they'd just drug me...
The quantity of medication we use, especially with kids, is highly unfortunate. IMO our biggest problem with our kids is that the knowledge of how to do things right really hasn't been passed on to the general public well enough for parents to make use of it. (And, in some cases, parents are a bit too lazy--doing things right requires planning ahead and being proactive.)