Honestly, the biggest reason I have not "already" switched over to a hosting service that specializes in DNN is the lack of disk space. With the low cost of disk space, why are hosting companies still offering only 512MB and & 1GB? A 5GB or 10GB site would probably be sufficient if I hosted photos and such on another service, but 1GB is simply too small.
For example, my work DNN site is sitting at about 4GB in use, and I don't consider it being used much at all, my users there are barely scratching the surface of what DNN is capable of. Currently my personal project site is sitting at about 150MB, and it is basically a bare-bones with almost nothing on it. Once the sites there get rolling like I want them to, that amount of disk usage will probably jump over 1GB in less than a month.
Then again, I don't have to worry about users right now because they visit once and never come back, almost always because of the horrendously poor performance. I'll get a batch of people all excited about the site, they visit and the thing crashes or hangs. I'll spend a day working with tech support and get it running decently again (only to return to this performance in a week or two), but the users are already gone, never to return. 99% of the time it is due to the performance (many of these people are personal friends of mine, and they certainly don't hesitate to tell me what is wrong). This vicious cycle has repeated itself constantly over the last couple of years, and across three hosting services. Right now I refuse to invite people to my website(s) until I can get this issue resolved.