Why? Pretty dumb thing to say.

It's best for all gamers. 

As long as it comes to the Switch, that's what I mainly care about :p

People say Nintendo needs more exclusives. When they do get them the same people say should not be exclusive. Exclusives is a good thing.

Didn't say they were, but hoping something is, is a different matter.

Either way, I'm just glad it'll be on the Switch as well.

Persona 5 is selling very very well (best Atlus launch ever), no need for ports, it will easily be profitable. We could see the future P5 spin off games on other platform though. The new SMT, on the other hand, is a lot more risky if it launches only on a console with an unknown (but a lot smaller anyway) userbase.

Makes no sense... if P5 is selling very very well (best Atlus launch ever) then why not put it on other systems? 

Because the public of persona 5 is only on ps consoles.

Japaneses games sales on Xbox one are a joke, and On a nintendo home console, it's the same most of time for every tiers game.

Then why bother with exclusives at all? When a game is exclusive to a console, one of the only reasons to go multiplatform post-launch is poor sales on the original platform, when you need more sales to be profitable. Not the case here, so no reason to break the 15 years old PS exclusivity, especially if it's for a few percents of the PS sales.

(One other reason for ports is the late PC ports, allowing some devs to charge full price again for games released a relatively long time ago. But Atlus never did it, so no reason to start now.)