For a lot of (I would even say most) people, sexual attraction and romantic attraction are separate. One might be sexually attracted to someone, but could never stand being in a romantic relationship with them. This is why approaching a complete stranger just because they are attractive is a terrible idea. Also, to the person you're hitting on, it seems like you are only interested in them sexually and not romantically, as it's impossible to get a good idea of a person's personality or to get to know them well just by their physical appearance.