There may be many reasons but you should not take it on personal level. Might be because of the taste, many women refuse to swallow it. Not everyone but there are some who loves it and they enjoy completely. But truly I know some women who just don’t want it go inside stomach. Though this may seem you sexy but all your enjoy can go off when you try to do it to your women and she does not loves it. So never try to do with your women if she does not like it and in fact some may act like swallowing just to make you happy. So don’t force your women or partner to swallow it, if someone loves it then its obvious you will enjoy more.