"The open source path" includes many steps before you actually see any source from people. Once they've released source, it's a little late to go back. But they might be turned away from going through the trouble and risk of releasing source in the first place if they perceive that Richard Stallman is the type of person they'd be appeasing.
But more to the point, Stallman does not just want open-source software. He wants free software, and just based on my informal observations, his ideas of free software seem to be losing traction these days. Yeah, there's a lot of open-source software, but BSD, Apache, MIT and other open-source-but-not-free licenses are taking the lion's share.
Even among projects that do use GPL, they mostly seem to prefer v2 rather than the more-free GPL3 and AGPL.