I've experienced similar over the years. I don't drive btw so it's not transport I'm asked for, but childcare! Living in a village and working term time only, in school hours, means I'm often the first person people contact if they can't make the school run, held up at work, older kids supposed to be making their way to their OWN houses after school only to find they've forgotten their key so can they stay at mine until their parents get back, etc etc!
Of course I don't mind helping in an emergency, and always do. I think it's the assumption that I'm always available that irritates me, the phone calls half hour before school run, 'Oh if you're going up can you pick up so-and-so as I'm running late, I'll collect her from you as soon as I can.' Or 'Do you mind holding on to my boys when school finishes, I'm running late but will be there soon!'
People are normally later than they say they'll be, kids often don't want to go home when collected so I can often find a couple of hours has been taken up, which I wasn't banking on!
I'm lucky, I know, working the hours I do but sometimes I feel like being totally selfish and saying 'No, this time is for me and my kids'. I rarely do though, if people know you're doing school run/going straight home it's difficult to say No! I can't pretend I'm doing something else either as somebody will see me, it's such a small place. So I sympathise with all you drivers who feel put upon at times!