I think both joeKnowledge and Bustin A Bogie have valid points.
Applications like Sysmetrix have more than likely seen more and more people leave applications like Oxygenator, QX, SkinMem etc as it's easier (and makes more sense I guess) to use the one application to do it all.
And even when skin suites were more popular, very few people, when considering how many skinners there are, actually created 'great' skin suites (IMO). It might be too big an ask for your average skinner to complete a massive skin suite.
I wonder if another Community Skin Suite could ever be accomplished and how many applications would be skinned today if one was started?