Then if you are Capcom, you go to Nintendo and say "Here is what Sony is willing to do with us. Can you match or better that?" If they say "no," you accept Sony's deal. If they say "yes," you go back to Sony and try to get a better deal out of them. You don't just sign a deal without seeing if you can get a better one.
That is a high risk, because of they did that, and didn't match Sony's offer, they would know what they are up to.
Next step, Nintendo knocks on Bamco's door, tells them the Sony Capcom deal and offers then a similar one for exclusive God Eater, with promotion and all, giving their direct competitor a great opportunity.
Because let's face reality, Switch is a much better console for MH like games than PS4, a million times better.
So you end up giving two choices to people, the game they want on the platform they don't want, or the copy of the game they want on the platform they want.
Could damage the franchise a lot.