They are the new flavor right now and many people prefer them only because they are dirt cheap. An atomizer normally sells for $10, with disposables they sell for $12 for a pack of 5.
The reason people like it is because an atomizers best performance is during the first week. The carbon builds up and the performance goes down. So you either live with it, clean it, or replace it. With disposables such as the Vapor King or the Nebula the atomizer is disposable but refilling it about 3-6 times is possible. See the posts regarding how to do it. The part that is good about disposables it by the time the atomizers is running out of refill ability, it is nearing the point where a regular atomizer is starting to get carbon build up and getting weak. So you really arent messing with the whole cleaning deal, you just toss it and put a new one on.