Besides, we've already got a bunch of really impressive ones. Like come on, mounted combat? What the fuck? That will either suck or else take a fuckload of work to implement.
If they implement it 1:1 with the tabletop rules it will be pretty underwhelming.
Most of the time it revolves around charging with a lance to get a lance damage multiplier then avoiding attacks to retreat and repeat. That is if some high initiative enemy doesn't just rock up to your mount and smash it in the face (You can do a ride check to try to avoid attacks directed at your mount, but the DC is the attack roll, so it's pretty easy to fail).
Also most people play halfing cavaliers if they are optimising, as halfings can actually fit mounted into most dungeons, unlike a medium cavalier on a warhorse.