Why is wanting to wait for marriage considered to be so strange?

I’m 25 and a virgin. I don’t plan otherwise until I get married. I’m also an atheist and am not doing it for religious reasons. I just don’t see the point of having sex with someone I’m not going to spend my life with and then moving onto someone else. That doesn’t appeal to me. I’m not a closet lesbian or a man hater. I wasn’t sexually abused. Why is this so strange? Most men move on after they find this out. My mom thinks I’m insane and tries to encourage me to go off from guy to guy like my sister who is 22. Will I ever find someone who can wait ? They don’t have to be a virgin themselves if they can wait.