Generally the two part belt is an inner that is narrow enough to fit inside of standard belt loops which you use to hold up your pants, and then an outer that is a little thicker that velcros onto the outside and buckles tight. Cool thing here is you can drop your belt and holster and still have a belt holding your pants up, but the belts work together when both worn, rather than wearing two incompatible belts, or one belt that is neither thick enough nor rigid enough to do the job.
Depending on what your range day looks like, you might be taking your rig off and on a bunch, and you don't want to have thread through all your belt loops every time.
It really depends on what you are trying to do though. IPSC guys don't usually care what their belt looks like, and are looking purely for performance. IDPA or other less fancy practical shooting folks typically want something that looks more like a normal belt.
Your average holster user probably just needs a good stiff leather belt.
If you are seeing lots of competitors with a similar belt, its probably because its one of the better belts for that application. Feel free to ask one of them how the belt works and where they will order it from. Most guys won't have any qualms about showing you.
