Basically nothing unless supply is limited or if the practice limits supply. Think of it in terms of prescription drugs for those on a fixed income or water in Ethiopia.

Specific to scalping, I'm sure it has to do with people wanting to be able to watch a show for $10 if tickets were at some point made available to the public for $10.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD