Because people want things like remote start, remote climate control, etc. that they can control from phone apps.
* Where's my car? Press the button, get a honk.
* Lock the doors. If they're powered, close themi first.
* Unlock the doors. If they're powered, open them afterward.
* Warm up the car, it's cold outside.
* Cool down the car, it's hot outside.
So that's five buttons on a remote, maximum. None of them require connection to infotainment systems.
* Lock button. Hold it down to get a honk.
* Unlock button. Hold it to get the car started; if the interior temperature of the cabin is outside a set range, warm or cool it appropriately.
Make one button big and round and smooth and bright, and the other one big and square and textured and dark.