well essentially you meet them and you form a reppore and desire for you, but there are so many factors that make that situation only applicable to that situation
over the course of a few days alot can happen and alot can change, she may forget who you are, the excitement and feelings obvsiouly fade and shes had nothing to keep it going, the date grows closer and suddently its more the case of"oh god im meeting someone i dont really know for a drink he could do or be anything or anyone!"
they freak and bail simply becasue they are scared or dont hold any of the orgional attractment, dont take it personally, just ask them nicely what the reason was, then ask if they can offer a resedual right there, and if they cant offer an excuse or a reschedual its liekly they are pulling your leg, just sa
"well ok thanks for telling me, just let me know wheny ou can meet up seeya"
then forget about her move on she probably wont text or call back, maybe she will if so awesome but otherwise failed.
they say only 10% of numbers you get will get responded to and 10% of that will come from a sinsear place! so dont worry about it at all!