While I do also have a Spotify Premium subscription, I am using it a lot less now than I used to. At least 10% of the album's I have simply aren't available on Spotify, and possibly never will be. Underground self-released artists very often don't bother with streaming services, or are outright against the entire concept in the first place, claiming that it devalues the music. It certainly doesn't pay very well. There's also the issue of music disappearing because of rightsholder disputes, such as most of the Motörhead discography being unavailable for an extended period of time. That sort of thing just isn't acceptable.
Honestly I've come to realize that I prefer a smaller nicely curated collection over a massive unwieldy semi-unlimited library, with questionable curation. I have reported hundreds of curation errors to Spotify, but they keep popping up, especially errors involving two identically-named artists being mixed together.
I will admit that I am very particular about tagging, labeling and sorting by genre. Spotify is woefully inadequate in this regard. For my own collection, I am in full control, which makes it much easier to sort and handle.