Depends on power. In MY OPINION......... I feel that if there is a little extra money, almost any bike can benefit from a lockup. Slingshots with a stock modded cover are pretty cheap. The benefit in higher powered motors is very noticeable slip reduction/elimination under WOT and the ability to tune the clutch for launch or slip out of turns for Trail/dune guys. My favorite thing about a lock up on a trail or dune bike is the ability to run way light springs and it lets it almost feel like a new honda 4 poke. My bike has a lock up, Barnett 3&3 springs, ASV lever, fresh cable, with a good basket and inner hub. People get on it and ask how the hell it even hooks the clutch up with a pull that light. But it works and it's nice to ride all day compared to 10 years ago where guys just stuck in the heaviest springs they could pull.
Guys will say spend the money elsewhere if the bike ain't a drag bike but look at the GNCC riders or MotoX riders, they all have lots of dollars invested in clutches designed to make riding easier, not harness high HP.