Sparring already has a lower amount of incentive than almost anything else in this game because you simply don't get anything out of it. It's also difficult compared to other aspects of the game that do in fact give you a prize for your effort.
So if something is difficult, and you have nothing to gain from it except your own gaming experience (which is probably nullified by frustration if you are losing 24/7 because you are new to spar) then why would anyone want to participate in it without a reward of some sort.
Add a tier system to not only add a small incentive, but also ease newer sparrers into action and also prizes? I think you'd definitely have something there that could bolster spar activity.