An immediate benefit I see is that they're cheap enough to use once - you could make/find/buy a software instrument that you like, then put it in your gear bag and never reflash it. Now it's just like any other synth. Then you can get a second Tulip and do the same thing later if you like. You could do this with laptops of course but it starts to get expensive.

The Pocket Operators have something similar (the KO at least, maybe the others). If you've written samples into them you want to preserve for playing live, you can snap a tab off and then they're read-only - no surprises on gig night.