what is it with some men?

My colleague just mentioned something which happened to her & has happened to me in the past with online dating...

Start chatting to someone, conversation is flowing...ye arrange to met & last minute they block u... no excuse of something has come up or whatever... twice it has happened when i've gone to the bar or wherever ye have agreed to meet & they just block u immediately without showing up?!

Its sooo rude & respectful....