why must i fix hole in garage ceiling?

i had my home inspection done, and there is a hole cut in the ceiling (roughly 12" X 30" of the garage that exposes some of the bathroom piping above (previous owner had some work done). He stated that to be up to code it must be sealed/patched. i'm just curious why? the garage is heated so freezing pipes won't be an issue. i will do it, but just wondering why it's such an issue. do pipes freeze that easily?

thanks

Didn't he give you any logical reason?

Building codes require that garage be completely sealed off from rest of house so that car exhaust fumes cannot get into living area. So this time there is a logical reason!

thanks for replies guys. i'll patch it.

not only do building codes require that no exhaust fumes from vehicles or other fumes from garage stored chemicals or gasolene be allowed to enter into the occupied area (living area) of a home ,but also that the wall and ceiling areas be up to fire code to slow the progression of a fire from the garage to the occupied areas ( typically at least 5/8" drywall between these areas)