There is two answer for this topic actually,

The Guy Will Expect Sex On the First Date

When:

1. The gurl have no potential to become the love of his life
2. The gurl look and appereance is not as the guy expected, this happen on a blind date, double date and etc
3. The guy definitely know that the gurl is after the guys money
4. The gurl is talking dirty during the first date
5. The gurl seduce her on the first date
6. The guy know that the gurl have been sleeping around with a lot of guys
7. The guy know that the gurl is easy to get in bed with.
8. The gurl is realy HOT and Sexy
9. The gurl have sense of attraction to that particular guy, for example; tough pierce
10. The guy is just a pig

The Guy Will Not Expect Sex On The First Date

when:

1. The gurl have a motherly characteristic, this impression will come to being a good wife and a good mother
2. The gurl looks like her mother: this will remine her of the guys mother and hopefully the attitude of the gurl will be similar to the mother, because the best women in a guys life is her mother.
3. The gurl is potentialy a wife material and up to the guy expectation
4. The gurl told the guy that shes a virgin, and the guy will expect to pop the cherry after marrying the gurl
5. The guy is not attracted to the gurl
6. The date just turn up good and the guy just go with flow and don't expect anything because he don't want to blow the date off.
7. The gurl is exactly what the guy expected of her and will just wants to start a relationship with her.
8. The guy find out that the gurl is underage, and the guy realy don't want to be involve.
9. The guy is gay
10. If the guy is a muslim, Usually muslim man and women will only have sex after they get married.