But it is much quicker an precise to do text selection with a mouse than it is to do it with a touchscreen.
True, but how much of time spent writing and editing a document is done in text selection? Besides, when I don't have a mouse available, such as while riding the bus, I can use keyboard keys to move the cursor by a word or line at a time. This works on my laptop's built-in keyboard or on a Bluetooth keyboard paired to my Nexus 7 tablet.
Not if you want to use a keyboard and mouse which is the optimal setup for FPS and RTS games.
Granted, that's fine for FPS and RTS. But plenty of genres that aren't FPS or RTS don't benefit from a mouse. Take a cooperative platformer for example. I don't see how a platformer would benefit from a mouse unless it's a Contra clone like Abuse. On a console, you'd put player 1 on the included gamepad and player 2 on another gamepad, either one sold separately or one included with player 2's console and brought from home. On a PC, you'd put player 1 on the keyboard and player 2 where? (It'd be possible to put player 2 on a USB gamepad, but only if player 2 learned how to play on a gamepad and not on a keyboard.)
Not everybody wants to sit within cable-distance from their screen with a mobile device
HDMI cable distance is pretty far.
much less have a cable hanging out of it.
People tolerate a cable coming out of a computer mouse.