because that sounds like shyt
this is an example of someone sampling and then PLAYING it themselves through the MPC
Craig Mack - Flava In Ya Ear (Origin) Full size High quality - YouTube
RZA did this a lot too, he would sample something, cut it all up on the ASR and then play it back in his own way with the keys.
people used (and still do use) samples because they don't have access to a band or people that can play a bunch of instruments. you think Marley Marl could get a drummer, bass player, etc all in his bedroom in Queens when he was making classic songs? it was a way to get more authentic sounds instead of wack ass drum machine stock sounds. you think labels were giving rappers huge budgets for them to get a gang of session players & studio time to record songs?