Which types of structural framing systems and materials are most commonly used in the US for residences? For office buildings?

What factors determine why these are the most used materials?

I believe that wood framing systems are the most commonly used for residential projects where as steal framing systems are typically used for office buildings. This is likely the case due to cost efficiencies.

Why do different teams of designers and subcontractors link and share their models during the design process? 

So that everyone else can see the design ideas of a subcomponent of the structure, without compromising liability constraints.

At what point in the project development process should design coordination start? 

Is it ever too early?

A lighter version of coordination I think could start at the beginning of the design process. I imagine it taking on the form of a discussion where certain parameters are set making sure that each respective discipline would run into less issues once a proper BIM Coordination takes place.