if you want to be picky, fair enough, perhaps "instrumental piece" would be a better term than "song". but a proper "piece" involves arrangement to make it more than just something that loops up and occasionally drops the drums. perhaps there are some "classic" beats that dont really take it this far, but i have never looped a sample and left it at that... i always build it up to make the track more involving. its not a matter of showing off my skills, but a matter of engaging the listener, as i have heard tons of people complain that bare loops are boring.
building up a beat includes, like i said, adding live instruments, introducing more samples, etc... and like i said, this can involve some serious technical intricacy (often more than if i had started with an original composition, as i have to deal with off-tune samples, roundabout tunings of my live instruments to match the key of the sample, layered samples of different keys/tempos that have to be adjusted to allow proper counterpoint and timing, and careful mixing when its all put together (the more varied your sound sources, the tougher the mixing process)).
unfortunately most of the beats on my soundclick page are live instrument beats (few sample beats) so i cant provide an example right now. when i get home tonite i will upload something that better illustrates this.