Why did Spotify deprecate basically half of the webAPI endpoints for developer mode applications?

[michiinya]

My Question or Issue

I've been working on a college project that is due in quite soon and I've been making it for months and out of nowhere it has just stopped working, turns out Spotify decided to revoke access to developer mode apps from these endpoints: 

1. Related Artists
2. Recommendations
3. Audio Features
4. Audio Analysis
5. Get Featured Playlists
6. Get Category's Playlists
7. 30-second preview URLs

These changes don't affect applications with an existing extended mode but I can't even qualify for it as my application is used for a college/hobby project. 

Why did Spotify just randomly decide to make all of these changes though, and why so suddenly? I don't recall any warning of these endpoints being deprecated in the future. I've seen replies to other posts about this saying that they didn't even know these endpoints were going to deprecated for their applications too, this just seems like a very poor choice that Spotify has made in my opinion.