Why are Pokemon sorted by CP in a gym and not by level?

It doesn’t make sense to me to sort Pokemon by CP in gyms. CP doesn’t really mean squat for battles, so why are the organized that way? Dragonite, Snorlax, Rhydon, Gyarados & Vaporeon are consistently top defenders, because of their high CP.

Organizing by level could prevent this and would allow high level Pokemon to also be able to be in a gym, regardless of max CP.

This could also add a variety of defenders into gyms like Chansey, Ditto, Blastoise, Venuasaur, Charizard, Slowbro, Poliwrath, Nidoking & Queen, Omastar, Victrebell and Vileplume that don’t typically make it into gyms or are bottom defenders.

I also think a prestige bonus who be a nice incentive to diversify gyms. 10% prestige bonus for adding a grass type, 15% prestige bonus for 6 Pokemon with different types, 25% prestige bonus for having 10 different Pokemon in a gym. This would make it easier to prestige, harder to take down, increase types of Pokemon and reduce gym stagnation.

The exact opposite could also happen, -10% prestige for having 3 of the same pokemon in a gym, -15% prestige for having the same top 3 Pokemon, -25% for having 5+ of the same Pokemon in a gym.