In some areas it is really hard to find landlords that take DSS. Where I used to live (Hackney in London) very few of the landlords took DSS. This was dun at least in part, I believe, to the lengthy time it took to process claims, and frequent mistakes which meant that landlords had to wait months to get a rent, which even then was by no means guaranteed. I have both claimed HB in the past, and am now a landlord who would not accept HB from a stranger because I don't trust Hackney to process it in a timely fashion, and I can't afford not to have my mortgage payments met! (I have accepted HB from a friend as a tennant, but he lost his job after moving in, and he's a mate so it's different!)
I suspect that in other areas if they process claims in a more efficient manner, you might find that landlords are more ready to accept HB.
Having said that, even in difficult areas, there will most likely be some landlords which accept HB, it's just a matter of finding them. I remember a friend of mine got a list of landlords which accepted HB in our area, but I don't know where he got it from.
I would start with asking the DSS and definitely also Shelter (the homeless charity) if they can provide such a list, they might be able to.
Try googling "landlords which accept Hpusing benefit" in your area, or something similar.
I expect most estate agents probably won't touch HB.
Also worth trying www.gumtree.com we rented a flat from a lovely private landlord we found through gumtree.