Sampling is cheap, easy, and essentially just stealing someone else's music.
This has been a complaint for decades: They don't use instruments! Sampling is stealing! But sampling doesn't define hip-hop, and vice versa. Sampling started with experimental electronic acts in the '60s, well before hip-hop began in earnest. And hip-hop is far from the only genre to use the technique. Justin Timberlake samples, Cher samples, innumerable EDM acts use samples. Even the Beatles went jacking for beats on their experimental 1968 cut "Revolution No. 9."
Furthermore, rap songs are often made without any sampling at all. The first hip-hop hit, "Rapper's Delight" isn't a sample of Chic's "Good Times," it's a band replaying it. Or check the recent commercials for Jay-Z's Magna Carter Holy Grail, prominantly featuring the three hip-hop production Hall of Famers who worked on the album. (And, for some reason, Rick Rubin.) Swizz Beatz, Timbaland, Pharrell Williams all blew up in the late '90s on the strength of beats that largely eschewed samples.
Then again, this whole counterargument needlessly cedes the point that sampling is a bad thing. Which is stupid. Producers like Marley Marl, DJ Premier and Pete Rock chopped, flipped, and manipulated samples, often to the point where the original song became unrecognizable. Their mastery of this new, distinctly post-modern form (making a new piece of art from a previously existing piece of art) proves beyond a doubt that sample-based music can just be just as creative, and often more so, than strumming four hackneyed chords on a guitar.
"Perhaps it's a little easier to take a piece of music than it is to learn to play a guitar or something," said Digital Undergound mastermind (and multi-instrumentalist) Shock G, in Benjamin Franzen's documentary about sampling, Copyright Criminals. "True. Just like it's probably easier to snap a picture with that camera than it is to actually paint a picture. But what the photographer is to the painter is what the modern producer, DJ, computer musician is to the instrumentalist."