My understanding is that, by volume, most people using Linux "in anger" (whose needs mostly dictate the direction of Linux development) aren't the SREs maintain

My understanding is that, by volume, most people using Linux "in anger" (whose needs mostly dictate the direction of Linux development) aren't the SREs maintaining living systems for years at a time; rather, they're the DevOps people with constant streams of greenfield projects, involving half-baked third-party components, that in turn need all sorts of random bleeding-edge dependencies.