Don't ask me, ask my guns. Bolt rifles don't need crimp, neither do ugly black rifles with proper neck tension. Leverguns and handguns seem to like crimps. Some handguns like a heavy roll crimp, others a light taper crimp, a few like variations in between. Cast bullets need a bit of a flare to aid in seating and a crimp die is often used to straighten up the case mouth but that may not technically be called a crimp since it doesn't actually reduce the case mouth ID past the nominal ID after sizing. Haven't seen the need for a Lee FCD yet but the concept interests me, just waiting for the proper situation.
The 22lr doesn't belong in this conversation. It's a heeled bullet and doesn't lend itself to reloading.
