How I see it [1], absolute values don't matter audio software, except when working with loudness compliance or some very technical things. What's important is how things sound, and it's generally a bad practice relying on UI metering to dial in sound in most cases. The typical audio work involves fine tuning parameters until things feel right. In UX terms, relative parameter tuning is the most common kind of interaction, and sliders absolutely suck balls at it, in my humble opinion.
Linear sliders actually have more inconsistencies across implementation than knobs, that have converged to more or less the same pattern. E.g. some sliders reset value if you click in the middle of it, at which point all prior tuning is lost - this is super annoying and I hate it. Others operate in relative mode and they're similarly intuitive in regards to which direction they should operate depending on slider orientation (should horizontal slider change its value with up-down movement? should interaction range extend beyond slider length?). Also, such sliders are identical to knobs, essentially, but take more screen space.
So, in a a nutshell, knobs are superior for fine tuning, which is 90% of all audio software interactions.
1. I'm not a professional, but I have clocked in thousands of hours into DAWs and other related software over the years as a hobby, also I played on a few local gigs and made some simple audio software.
