Mainly, this is because the IBC doesn't directly address the issue. Cabinets are not an "interior wall and ceiling finish" as defined by the IBC; therefore, the requirements for finishes should not apply. Also, the exceptions for combustible construction in Type I and II construction (Section 603.1) talk around cabinets (i.e. "trim and millwork such as doors, door frames..." and "Blocking such as for...millwork, cabinets..."), but doesn't specifically mention them.
In my 26 years, I have never been required to use FRTW in cabinets. I sort of consider them as "attached furniture."
My questions are:
1. If you're a building official or plans examiner, how do you consider cabinets? Would you ever require cabinets to be of FRTW? If so, what do you use as a rationale/citation?
2. If you're an architect or consultant, have you ever been required to use FRTW for cabinets? If so, what was the rationale/citation they used?