It doesn't really matter how much damage it would or wouldn't cause. If it were a military airfield in a conflict, they're be no problem : flights would continue unaffected and if one was damaged - very likely not fatally - at least the drone would be gone.
But a commercial airport ? If they keep flying and there's any damage, non-damaging collision, near miss etc. guess who'll take the heat ? The drone pilot ? A little. The airport operators ? A lot.