Anybody familiar with hip-hop music? i have a question about clean versions of songs?

I have some hop hop cds that are the explicit versions, yet they will have a song(usually at the end of the cd), that has a clean version of a song. Example, Wu-tang 36 chambers has a song at the end that has all the swear words cut out while the rest of the cd doesnt. Also Juric 5 has the J5 cd and all of it is clean, there isnt a dirty version as far as i know. Same with a cd called Hip-hop for respect-it's all clean. Dead Prez- has a remix of a song on the cd and it is clean. Why do artists put clean songs on dirty cds sometimes? Anybody have any ideas? Thanks