Where are the mods

Only certains have in-game mods.

That's the responsibility of the devs if they choose to use them.

I'm kinda lost as to what mods you are referring to.

Are you talking about mods for games, or some other sort of mod?

As a couple have said, this is entirely up to developers and since this comes up somewhat infrequently I'm not sure how much real demand there is. The support is certainly there if the game devs chose to use it.

Mods for games are fully up to the developers to put in. Skyrim and Fallout 4 have them.

If there is a game you would like to have mod support reaching out to the devs is your best bet to make that happen.

Okay then. What I mean by "Hidden mods" Is this thing where people use some thing called "XBL Stealth" where people mod and no one can tell if they are or not.