Because most people are not as saavy as they think, and expect apps to do things they aren't designed to do, or they can't figure out basic configuration.
The other day I have found really intersting site: Bad App Reviews - where there are only bad reviews. You can check you favorite application
For DLNA I use ArkMC applicaiton. I has a lot of useful functions and simple interface. And there is Free Version of it, so you can try before you buy!