There are straight out various achievements that gives mounts for winning, that's already a huge incentive. And the rewards from the match itself (not the roulette ones) also depend on your placement.
But sadly, people who only queue for xp would never find any reward big enough to warrant putting effort in something they hate.
I truly wish it was like pve where as soon as someone afks they're kicked and leeching is not allowed. The OP's proposal makes sense.
It's PvP, it's competitive by definition. If people don't wanna compete they can keep to PvE. Winning is literally the whole point of PvP.
Plus as I said above, good luck getting the mounts if all you do is lose.
