Most of you are far to young to appreciate how sweet hip hop was in the 80's and early 90's, anybody's songs were public domain to use as samples which created a limitless backdrop to any MC's rhymes no matter how much money you had you had a limitless supply of background for you to drop the hard rhymes without paying royalties to other artists. Just imagine for a second what P. Diddy pays to use 1 song in his ridiculous "music" and then imagine for a second what it would cost to make Paul's Boutique song by song. If you need help check out the song by song sample reference here :
Beastie Boys’ Paul’s Boutique Samples and References List
This is one of the very last albums where hip-hop was truly free
R.I.P