[asynchronous13]

> Does anyone know why this isn't standard?

Because cages weigh more. Minimizing weight is critical for anything that flies. If it weighs more, then it takes more energy to make it fly. If it weighs more, then that's less payload that it can carry.

[leetcrew]

it's actually worse than that. in addition to the weight penalty, prop guards decrease the performance of the rotors and make the aircraft a bit less stable.