I assume the UniFi NAS isn't meant for running Plex, for example. Most people seem to want a general purpose mixed media server, which can handle a bunch of data but where a good chunk of that data is movies/music/books that they want to stream. A good percentage of people probably also want to run docker containers. The $500 for (was it 7?) bays of storage is great, but probably mainly functions as a true NAS, so maybe not what a lot of people want. (I think the term "NAS" is a bit overused and can be deceptive for newer users entering the market)