It isn't, because development is upstream from UI/UX design. You can have a software product delivering value to end-user without UI design. Might not be pretty, but it'll do the job. Whereas you can't have a software product delivering value to users without development work. Moreover, it's the UI that's the direct point of contact with the user and the driver of sales, so the pressure to screw users over is higher there.

That's not to say developers don't make choices sacrificing utility for sales - they do, and I bitch about this here plenty (for instance: bloat, invasive telemetry, privacy-hostile solutions, addiction-generating mechanics). But it doesn't look like a trend that's essentially consumed the discipline.