Regarding the simplified question, blame the icon artist, an icon can be made to look great, just some people dont look at it as something that's worth investing time into to look great.
Also regardin the icon things, another thing to think about, MacOSX has alot of skins/themes that are pretty much inline with each other style-wise no? WinXP can get pretty different looking depending on your personal tastes, and in that sort of case, I'd prefer neutral-simple looking icons over colorful fancy/smooth-as-butter/shiny/glassy ones.
Also regardin the icon things, another thing to think about, MacOSX has alot of skins/themes that are pretty much inline with each other style-wise no? WinXP can get pretty different looking depending on your personal tastes, and in that sort of case, I'd prefer neutral-simple looking icons over colorful fancy/smooth-as-butter/shiny/glassy ones.