Yep. Either they provide mouse support or not. If they do, then the people unable to use a mouse and keyboard due to constraints, who don't own an extra mouse and keyboard, or who only want to use their controller won't buy this game.
They basically have to include controller support. The game changes so drastically in terms of the whole games layouts.
Including a mouse and keyboard version, the pc version, with 30 or so keyboard shortcuts and left and right mouse button setups while Also including the controller version, with less buttons meaning one button brings up a menu instead of having no need for a manu on the pc version.
It's simpler than I make it sound.
For example:
On the pc, O is to use a health potion, P is to use a magic potion, K is to open the map, L is to cast a skeleton, J is to cast a bahamut, U is to use an amplify spell or whatever, Y is to use a teleport spell, etc. This is all on the keyboard.
On a controller, you would have these mapped out in a menu, such as ratchet and clank or a quick select menu.
You would press Right shoulder button to open a quick menu of all the spells you have, then you use your cursor to select which spell you want to cast. Left Shoulder button will open up a quick menu which displays all of the creatures you can summon. X will open up a menu of all of your potions to use, etc and so forth.
these menus are not evident in the pc version.
That's just a small example.