Maybe it's because I'm a goyl, but 99% of people I approach at least reply to me. However, I do get a fair number of unsolicited requests, often of the 'hey let's RP' variety or asking for things that I'm not interested in, about 90-95% of which I turn down (I do always reply though, unless it's a repeat offender).
Of the approaches I make to people, I reckon it's about one third that go nowhere beyond an initial discussion/exploration, as one or the other of us discovers a deal breaker or decides it wasn't quite what we thought it might turn out to be be. Another third end within a few posts as it turns out not to be not what one or the other of us was hoping for, and about one third go on for a good distance (say, more than 2 months and a couple of dozen posts). I'd say that I end pretty much as many RPs as my partners do, though I try to always send a message to say so. Of those my partners end, about 70% are sudden disappearances/'ghosting'. My problem is periods of extreme busyness at work, during which I'm often not able to reply, and when I come out the other side, either I or my partner (again, about 50-50) are sometimes no longer as interested in the RP as we originally were. Games that survive those hiccups are ones that I cherish.
If guys are looking for tips on attracting more partners, then from my own experience can I just say have an interesting request thread up. I rarely post my own request threads as they lead to me being overwhelmed, overcommitting myself, and eventually letting people down. So I fish for interesting looking request posts and approach them.