Designed for portability in mind
As can be inferred from the design and added thickness alone, these types of shells are designed for those who plan to play the Switch primarily (or exclusively) in portable mode.
There's well fitting cutouts for every vent, port and slot, including the Switch's kickstand. Both the shells for the main Switch unit and the Joy-Cons may take a little bit of wiggling to make sure everything properly clicks in where they should. But once it does, the little nubs on the insides of the shells makes everything a snug and secure fit, that won't wiggle around annoyingly like many other Joy-Con shells.