Categorizing music - Is it really necessary?

[Lord Magus]

Labelling Music Genre's is important.
Not in describing what a group's "sound" is like... but in explaining a group's artistic "style" More often than not this remains a indicator of a given group's or genre's "sound" but there are certainly themes and even attitudes associated with genres regardless of style. hell, even appearance has a bearing on musical Genre's.
What was "Grunge" but a blend of heavy metal and hard rock sounds, only the performer's were generally seen in what looked like Goodwill purchased clothing, and often sang about morose topics.. grunge was an expression of manic-depressive teen angst, dressed up in dirty jeans and faded sweaters. Metal is more of the expression of rebellious teen attitudes, escapism, destruction, etc...

"Genre" and labelling of style is often more important to the artist attempting to convey something than the performer looking to make a buck, though in truth some styles sell better than others. this is true in any "artistic" media.
Look at the visual arts.. I bet there isn't a member of this board who wouldn't recognize an image drawn by Todd McFarlan as such, even if they don't know who Todd McFarlan is. The simple reason is his style sells.. so others emulate it.
Yet if I were to put forward an Impressionistic painting and a Pointelistic painting, most who didn't actually study art probably wouldn't recognize the difference. Primarily because, just as Grunge grew out of Rock and metal, Pointilism grew out of Impressionism.. so the two could seem very similar to the untrained eye.