Advertising for a lot of these books is on the author and their following- some of the large het romances get real ad campaigns from publishers but its rarer. A lot of it is like book tok word of mouth. TV shows otoh do actually get as campaigns so thats my guess.

I am so sorry people are being aggro at you for this; romance fans can be hyper defensive. The answer in short is men don't read as much- true for all fiction but its particularly dramatic in romance. Even gay romance authors who write for other gay men will have a reader demo of mostly women.