To be honest, there isn't really any reason to play Smash 4 today. All other entries have something to distinguish themselves:

-Smash 64: where it all began
-Smash Melee: the competitive darling
-Smash Brawl: the janky, odd, edgy, casual darling. Also subspace
-Smash Ultimate: the newest one, also the most satisfying to play (in my opinion

Heck, even the 3DS version is superior content wise because of Smash Run.

As a result, Smash 4 is the most eh, most irrelevant entry in the franchise.