Seems like there are now ~4 places to buy content (Oculus, Steam, Google Play, Apple App Store).
If you buy on Steam, your catalog is reasonably portable over time - you can buy another vendor's headset and still access your catalog. The cost is that you have to bring a separate device with you to host the catalog (unless/until the rumored Steam Frame comes out).
Oculus and Play are both based on Android. I suspect there will be e.g. guides on Reddit to sideload one vendor's catalog onto the other vendor's device.
I can imagine a world where someone prefers to buy content in one of these stores, to have everything in one place for portability to future devices. You're already seeing this in computer gaming with Steam (and Epic, Xbox, etc.).