Ah yes! This is an interesting board to come by. Myself, I find myself stumbling around the forum roleplay every now and again. I might not go looking for one there all the time, but I'll occasionally join one if there is one I am particularly interested in. Mostly I roleplay in-game, however. But I do find a few reasons for me to come here and burrow into Forum Roleplaying.
You see, I think that forum roleplaying is actually somewhat easier than in-game role plays in some ways. This is especially helpful to floofs who want to make something like a Wizard Roleplay, Mythical Creature Roleplay, Ranch Roleplay, etc etc. These all would require a healthy, functional website, and a complex map to be an active and functional group. However, giving them forum space is like giving them an open canvas. They can elaborately describe the roleplay they want, and the landscape you are in. Providing pictures and ideas. Sometimes this is much easier then making a big map and website. Additionally, people do not ever have to wait for someone to be on to post. They can simply post a good roleplay paragraph(or something in those lines), leave, and come back later to see what the person responded.
Over all, I think Forum Roleplaying boards add a nice addition to the Forums as a place to go when you have a great roleplay idea, but don't want to go through the trouble of setting up a website and map. I see many floofs hanging around there. Even if I myself am not around there too often, I find it nice to be able to jump into a roleplay like those ones. Plus, all the roleplays I see in those boards are simply imaginative.