Why do you think it's important to lose XP when losing a challenge?

Question

shouldn't the takeaway message of challenges be: if you win, you're rewarded.
if you lose, you've still learnt from it.
so why does it need to be punished? it grinds my gears to go backwards if I win ~60-70% of the time...

Answer 1

At times, the sense of defeat and its demerits are keys which drive oneself to work hard in order to stay away from it.

Answer 2

If you play vs much higher level player, the stake gets higher plus you might get bonus points for each answer. In the case of your loss, they still might cancel out the negative points. Or at least partly.
The system is thought up this way to get you moving ;)

Answer 3

because it prevents people who know nothing about code to get high amounts of xp over time