Paint on the outside of a tank is relatively easy to clean off.
You get paint on yer internals, all inside your airsoft mechanism that's gonna take a couple of hours to dismantle, clean and refit.
It's ironic really because airsofters had tried to move towards laser tag but the ranges are shorter and they don't work well in bright sunlight.
Airsoft, cheap, limited range, highly affected by wind, high impacting projectiles.
Paintball, expensive, messy and high impacting projectiles.
So really with the tanks for simulated munitions "laser tag" is the ideal.