'That was never my intention' as an excuse / get out of jail free card

Why does this come up so often? Ive seen it mentioned so many times and experienced it myself. You're open with your parent about how you feel (ie how their actions have made you feel) and you get 'I didn't mean to'. As if that absolves everything? If you hit someone with your car by accident, it still hurts them even if you 'didn't mean to'.

I feel like I've run out things to say to this. Why do they do it and what do they expect you to say back? 'OK then cool I'll stop being upset by your neglect / abuse / ongoing shitty behaviour' !?