The standard Xbox controller makes a lot of assumptions. It assumes you have two hands to hold it. It assumes you have two thumbs. It assumes you have a fluid range of motion to get to all of the buttons, that you have the reach to get to bumpers and triggers, and that you have the endurance to hold it.
And if you can't do any of that, there's a barrier that means you may not be able to play the games you'd love to play. That's why Xbox created the Xbox Adaptive Controller.