It seems that pretty much all music with any amount of popularity (at least here in the West) is available to be played on Spotify, unless someone has explicitly removed their songs - but notable examples of this (like Neil Young, famously) seem few and far between. This is despite numerous complaints from artists that they get paid a pittance even if their songs are played millions of times.
How is this possible? It seems like a bit of work and cost to acquire the rights to play even a single song in public - say in at a big event or in a movie. So I can't quite wrap my head around how they managed to convince all record labels and artists to allow their music to be played at will for such a tiny price!
Even if they did deals with some of the more popular artists to get them on board to convince others, one would imagine it would end up more like Netflix, etc. (i.e. a lot but not everything).
Was it just that they (the artists & labels) felt that they would earn even less money because of piracy if they continued to try and sell CDs, or sell their music online?