"The losing side doesn't need incentive to keep playing."

Warhammer.
Aion.
Basically any two-side PvP game or system ever.

There is literally no argument against losers getting 10%, 25%, 50%, or even 100% of the rewards winners get other than "I won so I want to be geared better and win more."

If PvP is about the spirit of competition, any attitude, system, or argument that supports a system that at its core stacks the chance of winning in any scenario to one team or another, the spirit of competition is dead. In a community that's already prone to being toxic, this kind of mentality only furthers that.

Everyone wins, everyone loses. There's literally zero reason to reward one over the other when you need both to have a game, when the rewards translate into actual power.