Physical media or not, you are purchasing a license. A license to use the content for your personal entertainment, that is.
By re-selling your physical media, you also re-sell that license. That's why your right to use the content goes away with the physical media.
You can't re-sell your download, because the license to the use of the content is connected to your account, and with that, to your person. One could imagine a future where the re-sale of a download might become possible if the original seller would offer a way to transfer your purchase to a new account. But while that might be technically not all that difficult to implement, I wouldn't exactly hold my breath. Any re-sale, while legal, is seen as a lost sale by the industry, as they'd rather sell two licenses to two different people as one license to one person that later gets transferred to a second person without them seeing another dime.
The exact same concept applies to software, by the way. Regardless of whether you bought your game, your operating system, your utility application, or whatever else, on physical media or as a download, you have not actually purchased the software itself, but a license to use it. The software itself remains the sole property of the developer. Or their distributer. Things can get a bit fuzzy at times in this regard, but the point is that you never purchase the software (or movie, song, book, etc.) itself, but a license to its use.
Once I (who, as a teenager who got a letter from a lawyer about my alleged *cough* use of peer-to-peer sharing software, felt motivated to read up on these things) realized that you don't actually
own the content—be it on physical media or as a download—but merely a license to its personal use, it made the switch to go streaming only rather easy for me. The usual—and somewhat understandable but not exactly legally correct—argument that "owning the LP/CD/etc means that you outright own the content" simply didn't do it for me anymore.
And so now, I see my streaming subscription as what it really is: A frankly ludicrously low rental fee to a planet-sized library of music that I can browse and consume at will.
Do albums I have bookmarked disappear on occasion?
Yes.
Does my access to the content cease the second I stop paying for my subscription?
Also: yes.
But since I never actually
owned the content on all those LPs, CDs, cassettes, DVDs, and VHS tapes that I bought over the years to begin with, the whole concept of subscription fees and streaming libraries just feels much more true to the original intent and feels, as such, more honest to me.
Which, of course, isn't to say that you shouldn't buy or enjoy your physical media or downloads. This is simply my personal perspective on these things and by no means should this keep you from doing what you enjoy. To each their own.
Plus, buying physical media (and downloads) is—and will likely remain for some time—one of the more effective ways to support the artist. So it definitely has that going for it, too.
Disclaimer: Not a lawyer, just an armchair philosopher.