It’s not about *assuming *randomness or chaotic behaviour, it’s that models that include these features make good predictions. e.g. we can predict very precisely the frequency with which electrons will tunnel through a barrier.
(OK, I know with “randomness” there’s a degree of interpretation involved and it’s possible there could be non-local hidden variables. Half Man Half Wit will know better than me.
But I’m not aware of any effort to interpret away chaotic behaviour. Or anyone that claims it breaks physical laws.)