There may be a simple explanation. Samsung has already revealed that it’s teaming with Microsoft on a game streaming experience that should debut later in 2020. It wouldn’t be surprising if Samsung saw that as more viable and decided to shut down PlayGalaxy Link to avoid duplicating efforts.
Samsung’s service already faced stiff odds. Between direct competition like Valve’s Steam Link as well as subscription services like Google Stadia and GeForce Now (which have their own share of problems), there’s not as much need for PlayGalaxy Link — especially when others aren’t as closely tied to a specific phone brand. The Microsoft collaboration could lead to a better service that stands a greater chance of competing with incumbents.