I am so with you on that, Rowan. I feel the need of being kept in touch, to me it's proof I'm being cared about.
If I was told by my boyfriend "I'll be back by/at 11:30" and things changed, I would expect them to call or text as soon as they figured out they can't make it, which is whenever they would have left otherwise. So, if they're 20 minutes away from our place, I'd expect a call/text at 11 if they're not on their way yet (a little bit extra room in case there was traffic, etc), telling me what happened, or just that they'll be late, the details don't matter that much.
If they realise they're late and didn't see time fly, I'd expect a call/text "didn't realise how late it was, I'm on my way now", and not just for them to go straight home.
A lot of the time, my boyfriend doesn't really get that. I end up expecting him at a certain time, and he isn't there for various reasons. If I call him he explains what's up, but if I don't call him he figures he'll have time to explain whenever he sees me next. It's not a huge deal but I hate not knowing because I always assume the worst (there was an accident, etc).