Well, I'm not the main guy behind RFB, I just provided the Truk Atoll mod for it. I however got the "go for it" to host it here in SHMF. And the reason for it? Well, I don't KNOW it, but AFAIR it was something about my dedication to the ENTIRE Silent Hunter franchise, not only SH3 or SH4, but both, plus the upcoming SH5.
The former sticky threads at subsim got unstickied, and then got a link inside one sticky, so the threads for most mods can be found. Otherwise all forums have a search function too.
SHMF is also collecting the SH4 mods in a slow but steady speed. The major mods are here, FOTRS is hosted, I just wait for MadMax to sign up. Ducimus don't visit often, he has another forum, where he resides mostly. Lurker the same for OM and RSRDC. Luke has just made a visit, and he knows RFB is here. Webster has his GFO mod here too. And then some smaller SH4 mods are here too. And then I haven't even mentioned the SH3 mods yet.
But SHMF faces the same problem: the modders are not that keen to secure their mods anymore. They publish it through their own filefront page, and then after a while it may be lost because they don't respond to filefront's mails about deletion. This is one of the reasons why I expanded my site to host more than just my own mods. But what can one do, if the modders don't want to make their mods hosted themselves, besides asking them if it's okay to secure them for them?