There’s also the issue with different services using different methods to normalize their audio. In the music world, Spotify is pretty widely known to do some weird fuckery to your LUFS. Oftentimes, musicians need to send different versions of their songs to each service, mastered specifically for that particular service, just to get a consistent listening experience across the various platforms.

It’s a lot of extra work, just for the sake of consistency. If you have something like a podcast that is on both YouTube and Spotify, it will sound different on each unless you go through the work of normalizing for each one individually.