There is no rule to making music and there is no rule to using the MPC.
It all depends on what music you make..you may find the old skool style hip hop guys to be more sample based thats not to say they will limmit them selves to just that, jungle/drum and bass is still heavly reliant on sampling for that Ahmen break and so on.
Electronic music tednds to be a bit of a mixed bag, I have to say I dont sample other peoples work 90% of the time when I'm writing a house track but I will sample my self etc use creaive sampling techniques weather it be with my MPC, EXS in Logic or both.
But I like all types of music...but I stick to what I love and know best when it comes to making lol I wish I could bang out some Pete rock shit on my MP or some Photek type stuff but it just aint gonna happn.
Here is something all by me not using other peoples samples, MPC is also playing 2 synths that are out of the shot.
http://uk.youtube.com/watch?v=WrWDW-Du-s8Stuff Used:
roland jx-3p > pad
roland alpha juno > bass
roland tr-707 > cymbals,high hats,rim
For the glassy synth I sampled various keys from a EMU Proteus2000 module.
The TB-303 sounds is from rebirth which is running as slave to the MPC master midi clock
All the hardware synths and machines are beeing played live over midi from the MPC.