I don't crimp my match ammo. I have been thinking about trying it, but I like winning money with my old standby loads with no crimp.
Only things I don't crimp right now is my 30-06 reload for my Garand, and that has as much to do with the fact that I'm using bullets with a cannular that is placed for proper cartridge OAL for 7.62 Nato. I also don't crimp my handloads for my Savage 10FP.
I use a light crimp on my .223 for AR now to make sure I have fairly consistent neck tension, and to help add a little added piece of mind that during loading into the chamber (nose of the bullet is rammed against the feed ramps) that I don't drive one in too deep on a loose case, and get an over pressure. Odds are slim, but it just takes one.
For the same reason, and to remove the flare on the case rim, I crimp my handgun rounds.
Most seating dies can crimp at the same time, so it doesn't add any time to the reloading process.
If you're worried about this with an AR, your butt must be clenched when you shoot your Garand!
The Savage will jam a bullet also.
I still say only crimp in tubular magazine firearms