I don't cringe or get annoyed in any way over someone else's ends. I have enough problems maintaining my own hair, let alone cringing over someone else's. I generally can't even see if someone has split ends unless the damage is extensive. For instance, the whole length is damaged from excessive heat, coloring, bleaching or relaxing incorrectly. In that case, I sometimes briefly feel sorry for the person that they don't know how to take better care of their hair. But hell, maybe they like it like that. I don't know.
As far as thin ends go, I also don't care. I guess I'm not one of those people who cares much about perfect hemlines. I think I feel worse for people who get trims every 4-6 weeks and can't understand why their hair "never grows".
In any case, even if I thought someone should get a trim, I wouldn't say it to them unless they specifically asked me.