Because photoshop is primarily a complex software for professional raster image editing/designing. Those who use it for that purpose will not think of Figma as its replacement. Figma is a SVG based UX design tool and those who do UX design in 2020 most likely (hopefully) aren't using a heavy/complex raster graphics tool like photoshop.
No, I understand and agree with all of that, I sometimes design UIs and I wouldn’t touch PS with a laser pointer for that purpose.
But the article talks about software from 10 years ago to now. I remember even as Sketch had been rising for a while, something like 52% of UI designers still used PS. Pretty sure that wasn’t even close to 10 years ago!
So I guess that’s why I thought PS->Figma was a reasonable jump in that context. Even if they used Sketch in the interim or whatever.