I always assumed that the streaming services had negotiated to receive DRM-free versions specifically to avoid this issue, similar to the DRM/telemetry-free versions of Windows used on air-gapped government networks.
Google stadia had special builds, very well could have been DRM-free.
Other streaming services like G-force now are closer to renting a virtual machine with some automation scripts on top. Where after connecting you use a slightly modified version of steam to install games (which publishers allowed to be streamed) almost like you would install them locally. Those definitely aren't DRM-free (except a portion of indie titles which are DRM free everywhere). While G-force now tries to limit access to underlying OS, surface is too large to trust the platform with DRM free builds especially if it allows installing multiple games and steam workshop mods. It's a bit more complicated as g-force now also has "ready to play" games which provide more stadia like experience with better integration.
So overall it means 2 cases: * special builds/game specific integration scripts from streaming platform -> requires extra work and agreement between streaming platform and developer/publisher, introduces uncertainty of how streaming platform limits account sharing (compared to the DRM publisher uses) * no extra work, just single checkbox in steam developer panel -> potential conflicts with finger printing, DRM and anticheat systems
Neither of 2 are no brainer free money. Either it's extra work and bureaucracy to negotiate, prepare and configure special build. Or it's conflicting with DRM systems.
It's trivial only for smaller indie devs who are uploading DRM free builds to steam anyway.