It used to be (and still is for a lot of us) a bandwidth problem. If you don't have much, you won't burn it all up for the other guy. If it takes 4 HOURS at your full bandwidth to upload a file to a DD site, you probably won't do it, and a reshare just isn't going to happen. As pop mentioned, most downloaders only take, never contribute, and they'll NEVER make the effort to upload to a DD site. With eMule, that doesn't matter so much because
while they're taking, they're also sharing, and a new file gets distributed faster.
Older files that don't have a lot of demand are transferred at a much slower pace, plus the uploader doesn't have to do a damn thing but use some hard drive space. Files tend to stay around a long long time - YEARS even - and reshares are as simple as copying the file to a folder and clicking the Reload button. If you have low bandwidth you can throttle eMule and use the internet even while up/downloading.
It's easy to find stuff you're interested in. My interests are varied, from the type of films we have here, to firearms, to literature, to how-to, to... you get the idea. eMule's search is pretty good and I've dug up lots I'd never have found otherwise, especially if you use NOT and AND to help weed out the inevitable porn.
Most DD sites require you to register and the owners almost always have a thousand advertisements to pay for it, not to mention the scripts running in the background to maybe infect your computer. The ads make every page take 5 minutes to load with my bandwidth and most of these sites require you to disable ad blockers and script blockers. I refuse to open my system up to attack. I've gone many many years without my PC getting infected, I'm not going to start now.
We've been using eMule for a long long time and it works well for us. Maybe things will change in the future, but for now this is an eMule board. Nothing's stopping people from using other methods, but until/unless a film is available on ed2k, it's simply not an FLM release.