Are you also incapable of telling people that you won't be on time? You seem to articulate it fine here.

If you tell me that you'll pick me up at 5pm, but show up at 7pm... I'll be upset most likely. But if you tell me that you'll pick me up at 5pm, but will probably be late, maybe even hours late... I'll get it... And will adjust accordingly (most likely I'll get a ride with someone else if at all time critical).