I beg to differ about them jamming up ... we fix a number of stuck lever action guns every year.
I've got a 1968 Marlin 336 30-30 that was handed down to me, I've been shooting it on and off for years, took my first deer with it. Never had any issue until a month ago when the lever got stuck on me. Had to bring it home loaded, wasn't equipped to work on a gun that day. In my mind it was a complete catastrophic failure. Had I really needed the gun it was completely unusable as anything more than a club, it wasn't just a jam that could be cleared it was completely seized. I still love the gun but will never fully trust it again, I now realize how common it really is.