We're in a world where most people predominantly use proprietary software on proprietary operating systems. Many people are tied to those platforms because key

We're in a world where most people predominantly use proprietary software on proprietary operating systems. Many people are tied to those platforms because key parts of their workflows keep them from migrating - in this case, people who use Adobe's tools as their daily drivers would have a hard time moving to Linux. If Adobe made their software available on Linux, that would allow many people to migrate, which would in turn help expose those people to lots of other F/OSS software, which would then build up their userbase over time. None of this would happen instantaneously, of course, but there's a precedent for this sort of "small" change causing large shifts. For example, OS X having a unix foundation was the trigger for the gradual (but eventually large-scale) move of software developers towards macs.