That's what I think too. I'm not a big sports bettor but when I do it is mostly because I will watch the match and I want to increase a little bit the thrill: we always have a team, player, fighter etc. we want to see winning, and that's enough, but adding a little extra prize to the equation makes sense.
What doesn't make sense to me is betting in non-pro sports you don't understand or you don't mind even watching, because it is like pure gambling, and I think that there are better games for that.