im a gc and i hire demo contractors for everything from clean out to large demo jobs...in some cases i even do the work myself but wondering if the end users here actually hire demo contractors or just leave it to the gc

I usually leave it to the GCs. 

Recently, I foolishly thought I could just hire "some guy" to demo my last project, not knowing you had to have a permit in Tampa even for a simple drywall demo, and I got my clock cleaned by Code Enforcement.   Now I just leave it to my GC.  

I actually prefer to do it myself (with my team) for two reasons.

First, one demo mistake can be incredibly costly.  Water + electricity + cheap labor and Sawzalls = bad.  

Second, the walls speak to you during demo.  Telltale cracks, old, poorly done renovations and patches, original construction defects, water damage...they are all information which helps me adjust my build plan if needed.  If you just walk into a clean site, you can miss all that.  @James Edward