He is not interested enough.
Or he is afraid to make a move.
If it is the latter, you can push him over the edge by taking an initiative yourself, but I doubt you want to take a risk of rejection or the risk of dating a coward. When you two are emailing , he would make a move (invitation) already.
Bottom line: Not interested or pussy.
To make him more interested, you can send him photos of you in lingerie. If you willing to make that risk. I dont recomend it though.