Why do women give out their phone number to guys they are not interested in?

My girlfriends younger sister has been complaining to her that 2 guys from her college keep phoning and texting her to hang out with her and she is not into them and is considering changing her number because they are bothering her to hang out.

She was complaining about it in front of me the other day and I took the side of the guys and said to her it was stupid to give out her number and lead these guys on and then just ignore them. I told her it's rude to just ignore these dudes and she should at least explain something to them rather than just ignore because if it was me i'd be taking a chick handing you her number as a sign of interest.

I don't understand why girls give out their phone number to guys and then whine about it when the guy tries to contact her. What else did you expect him to do with the number? Just stare at it? lol

Why not just make something up? Anything? It's not that hard to not give out your phone number. I refuse to give out my number to people all the time.