Sex on the first date means that the woman found the guy interesting enough and sexy enough to try making an investment in intimacy with him. It doesn’t always work as sometimes she finds that guy is not so good in bed, or sometimes he is so much of a cad that he then looks upon her as cheap after the fact.
The dynamics are different from one person to the next. Many women do not chance that level of intimacy until several dates have passed. I tend to interact online with people before meeting them, resulting in an understanding of whether we are getting busy anytime soon. Because I’ve had long distance relationships over the decades, meeting may well go straight to the bedroom because we have already done the equivalence of several dates online or over the phone.
None of these women have been in any way cheap.
If anything, these are women with their social interests sorted and their confidence in themselves established, and a sophisticated enough understanding of their sexuality to know how to enjoy that part of who they are with someone to their own benefit, knowing full well that he will also come away happy. To me, that sounds like a great partner.