VFP DLL's and COMs

I've reading on Visual FoxPro lately and found out that it is possible to Build projects into DLL's which I thought previously was not possible.

Could someone answer why most of the time when we talk about DLLs and COMs, we use VC++, C++ and VB, and not VFP?

What are the advantages and disadvantages of creating a VFP DLL and COM?

Is it possible to create a DLL or COM in VFP that would access a Visual FoxPro Database (.dbf) and then build it as a DLL or COM and then access the DLL or COM in VB?

Would it be more efficient than using ODBC?

I would want to avoid using ODBC since you would need to create DSNs for ODBC before it is possible to access the database in VB.