Shit like this happens because many folks (men and women) lack assertiveness. Assertiveness is saying "no" when you mean no.
"no, I don't want to go on a date, there are cute chicks over there, try them".
"no, you can't borrow my chainsaw, coz you broke my lawnmower the last time you got it".
"no, I don't want another beer, I am driving home".
I have done an assertivenss course which teaches you to keep saying no until the person gets it. Westerners are taught that saying "no" is rude and you should always accede to a request. Therefore, they will make an excuse rather than say "no".
I had a roommate who was from Ghana and lots of folks thought he was rude. If he wanted something, he would ask, because Ghanians apparently don't have a problem saying "no". He asked me if I could fix his friend's computer, I said "no, I don't do fixing 'puters, because otherwise I would become the unofficial university computer technician, so you'll understand that I can't do this, plus, I'm crap at that". He was cool with this.
Folks who are naturally assertive have trouble understanding what the fuck is up with the excusers, however, it can take a bit of self-confidence to learn to say "no".
Many guys are this bad too - "I'll call you tomorrow" - yeah, right! Basically, people are spineless and many of them suck.