Aside of political motives regarding Microsoft, the technological problem that Valve is solving with using the flatpak technology is creating a single Linux build target for all Linux game releases.
A recurring complaint from gamedevs is that it's difficult to support many different Linux distributions/versions/runtimes. Steam already does a decent job providing its own runtime to link against, but this goes several steps further in abstracting away from the distribution that a user may be running.
Aside of political motives regarding Microsoft, the technological problem that Valve is solving with using the flatpak technology is creating a single Linux build target for all Linux game releases.
A recurring complaint from gamedevs is that it's difficult to support many different Linux distributions/versions/runtimes. Steam already does a decent job providing its own runtime to link against, but this goes several steps further in abstracting away from the distribution that a user may be running.