Sony's Playstation Now, Nvidia's GeForce Now, and several other platforms have been growing in game streaming space. Gamefly's long-running game streaming service shut down last year after EA's acquisition to be reborn as Origin Access Premier. However, each of these options suffers from restrictions of what games can be played and the hardware it can run on.
By contrast, Google's Stadia works on hardware consumers likely already own. It has been demonstrated to work on phones, tablets, Chromebooks, PC's, and even the $70 Chromecast Ultra. Compatibility with Apple devices is still a question mark, but the limitation is unlikely technical. Apple's App Store policies prohibit apps from selling digital content directly, as Spotify is well aware.
The ubiquity of compatible hardware dramatically lowers the barrier to entry. Customers do not need to carry a dedicated device with them to game on the go, they can merely use what they have at the time. Users can also hop between devices on demand and pick up immediately where they left off.
The largest obstacle Stadia faces for adoption is the same unavoidable obstacle all game streaming services run up against. Users need a reliable high-speed Internet connection. That is going to cut the service off from a significant portion of rural America and much of the world. Unlike Microsoft and Sony who faced resistance with the idea of game streaming in their consoles, Google is not entering this space with a dedicated following to upset.
There is another aspect to the datacenter-hosted game streaming model some have objected to. By its nature, users do not have access to game files. On the one hand, this can virtually eliminate many hacking tools that allow users to cheat. On the other, it prevents tinkerers from modding games which can be a valuable learning tool for the next generation of game developers. More commonly, users cannot make configuration edits to improve the game experience beyond what the in-game settings menu allows.
Realistically, we do not see Stadia - or other game streaming services - supplanting PC gaming, so these criticisms may not hold much water. Instead, Stadia is well positioned to carve out marketshare from the console market if it can succeed at delivering the highest quality graphics on any platform with low latency given a reliable connection. It is a tall order, but if anyone has the infrastructure to deliver, it is Google.