Replying to Forward Lean

I noticed my full tilts came with alternate plastic risers to add more forward lean. The question: GENERALLY, what is the purpose of additional forward lean? I've tried them out, and it makes my stance a little better, but it feels more exerting. Maybe that's a good thing. For park I've taken the inserts right out for less lean than normal, but it was not too noticeable. Is it simple personal preference on adding more lean or not? Please only post if you know what the hell you are talking about, PLEASE