I find it sad skins for modern widget toolkits and desktop environments are much less numerous and seemingly much harder to make. It was so simple and cool with WinAmp. Why can't we do it this way today?
Branding. Winamp was in a unique era where companies were just happy to have their software be used, and everything wasn’t about growing/expanding a brand for eventual sale to a megacorp.
I don't understand how does this particular thing prevent people from making more Qt and GTK themes though.