I don't crimp, but then again I don't load many bullets that have the cannelure to crimp into. I'm not against crimping, just that I get acceptable accuracy from neck tension on HPBT bullets.
The one rifle I have that could benefit from crimping is my 308 Saiga, that action cycles with enough force to unseat the bullets. Nothing like having a misfire and cycling the action back and having a loose bullet and powder fly everywhere. A couple years back I saw some pics of a firefight between two cartels down in Mexico, and there were AK bullets just laying on the ground, obviously not having been fired, the brass from the fired bullets showed that they weren't using milspec steel cased stuff, and the obvious answer is that the AKs were having malfunctions and the thugs were clearing malfunctions and leaving emptied brass, bullets, and powder on the ground.
Machine guns are awesome until you have to carry one.