Israeli forces use Krav Maga for peacekeeping ("peacekeeping," anyway,) not just armed military engagements.

MMA has a lot fewer rules than, say, kickboxing, but practically every illegal technique is useful in some way (otherwise there would be no need to have a rule against it,) the matches are fought in rounds, always against a single opponent, with a referee who restarts the action if the combatants reach a stalemate on the ground, in a ring with plenty of space to maneuver, no obstacles or potential improvised weapons, and fighters have months in advance to research each other's fighting styles and plan countermeasures. It's not as if MMA constitutes a particularly rigorous investigation into the optimal fighting style for personal self defense.