You can create multiple libraries to clean up different type songs, etc
iTunes is obviously in favor of this since they added the feature
I understand I can put the music into a playlist; I did that years ago but as a library gets bigger and ALL songs are in one library, you are dealing with all the songs vs putting say, holiday music in one folder and just seeing those songs during the holidays
This is a iTunes SUGGESTION on their support site
So to answer your question of WHY, because I can.....
How about an actual answer to me specific question in lieu of a lecture and silly questions