Very often stuff is saved off YT or SoundCloud and put in various folders likely to never be sorted. I don't know if this is true for others, but the way my playlists come into existence basically involves me playing a lot of different music from a whole bunch of places and if I think one random thing sounds good with another thing I have them play next to each other, and this process repeats slowly over time until the playlist gets pretty long (50+ items avg) and everything is in the order that I like it.
