Who said that Spotify is the endgame? That's like saying that MySpace is the endgame for social media or that 3Dfx is the end game for GPU tech. Few tech companies survive long term. AFAIK, unlike Netflix, Spotify don't own any of the IP they stream, they just license it from the major record companies, making them effectively just a middleman with commodity tech. So, in theory, if they wanted to, the major record companies who actually own the IP Spotify streams, could join forces and build their own streaming services, and stop licensing their IP to Spotify, effectively killing them over night. And let's not talk about the bad blood between Spotify and many artists who would love to see Spotify burn to the ground.

So, IMHO, in theory Spotify is even easier to kill than Netflix, but as to why that hasn't yet happened, that's up to the execs of the major record companies to answer. Maybe they decided it's easier and more convenient to just sit on their butts and license their IP to Spotify, Apple, Amazon, and have them outbid each outer for the licensing fees and collect rent from them, rather than bothering to assemble armies of picky and expensive SW devs to build their own competing services, since those dinosaur execs at the record companies aren't known to be very tach savvy, and in fact spent most of their lives fighting the tech industry in courts instead of investing in it.

Also, most importantly, music and video distribution and consumption are completely different beasts, so direct comparisons between Netflix and Spotify are pretty difficult even if all other things were to be equal.