Of course as a single customer I can't speak for the reasoning behind the decision, but I am saddened by it. I've really grown to enjoy using Substance Painter .... and actually can't imagine NOT using it as it's sped up my workflow so much. However, if Allegorithmic goes down the Adobe parasitic subscription road (with no perpetual licensing), I will likely move on to something else - perhaps Mari - as I refuse to *rent* software.
I hope that Allegorithmic understands that many of us in the community have been around long enough to see larger companies buy software either to abandon/sit on it, kill it outright, ruin it with bloat, or make the licensing/prices go from reasonable to onerous .... so the tremendous lack of trust isn't unwarranted.
This reminds me very much of how I felt when I heard that my beloved Softimage was bought by Autodesk .... who SWORE they didn't buy it to kill it ... and we all know how that turned out ....