JDate and similar sites aren't exactly religious. There are lots of secular Jews who would prefer to date or marry another Jew, for ethnic, cultural, or national reasons.
True, I think part of the confusion stems from the fact that you can have "secular Jews," since the Jewish way of life seems to be a bit more than just about religion (not saying the religion isn't an important part of it). If someone were to say "secular Christian" I'd look at them funny.