Reading yet another bridge thread this morning, and realised that in nearly every thread about mechanics, e.g., the various Badass v BBOT, through-neck versus bolt-on, tone woods versus whatever the opposite of tone woods are, and even about the basses themselves, sustain is often the characteristic of the bass that is discussed. But why? I get it with, for example lead guitar (although for rhythm it's often completely undesirable), and I get it with some orchestral instruments, although in many again it's undesirable (and I'm prepared to be told I'm wrong, but I assume that with many instruments it's de facto undesirable, for example kick drum)?
Anyway, I've realised over recent years that I've always been impressed by sustain on a bass, as if its capacity to sustain was somehow a mark of superior quality build or components, but that I rarely, if ever use sustain, even on fretless. In fact I use foam mutes so often that whilst being impressed by an instrument's sustain in principle, I often immediately inhibit it.
So, genuine question, why is this? Is sustain just the Emperors' Invisible Clothes, or a legitimate mark of quality?