It wasn't always like this. When Spotify was launched the desktop app was one of the best pieces of software I'd ever used. It launched quickly and songs played without buffering which was unheard of at the time. It was the work of largely one developer, Ludvig Strigeus who was also the author of the original uTorrent client (which was also used to be fantastic). As a software developer I'm biased but I think this ultra smooth experience was a large contributor to Spotify's initial growth.