I've never used a belt either, and never thought I would use one.
What's is the point when you should use one for safety? When you get up around 1.5 body weight? Less? More? All the time, regardless of weight?
And for what execises? I can't imagine now using one for Squats or Deadlifts, but Push Presses can sometimes be a little dicey if I don't concentrate. Then again, in the future when I put up bigger weights hopefully, I should expect to use them for Squats, etc.?
Bottom line, when should you even use them?