I never understood and never will understand why Sakurai chose Lucina & Dark Pit over Young Link & Pichu as clones.
You never understood?....................................................................................................................................................................................................................................
...Dude, first of all, Toon Link is already a part of the roster, second of all, Dark Pit & Lucina are from popular 3DS games from hardly years prior.
Where does this "This character got in over that character" mentality come from that so many smash fans seem to have? It's like you're proposing that Young Link & Pichu were ever on the table for Smash 4 to begin with. How can Dark Pit and Lucina be chosen over someone who was never intended to be in the game.
The reason they are separate characters is because they were originally planned to be costumes. Young Link & Pichu can't be costumes of Link or Pikachu. If they were intended to be costumes, then they would have made it into the game like Dr. Mario did when he was intended to be a costume for Smash 4.
It's not like Sakurai was sitting there like "Hmm. We need some clones. Who should I pick?" The clones were later additions that came naturally when it was decided they couldn't be costumes. But, even if he was, Lucina and Dark Pit are just logically better additions than Young Link or Pichu. Though I think Pichu should come back in the Switch game. Not sure why people would think Young Link should.