Why can't you run Romex in conduit?

Romex cable cannot be run in conduit because it is not designed to be used in that way. Romex is a type of non-metallic sheathed cable that already has its own protective outer jacket. Running it in conduit can cause overheating and damage to the cable, potentially leading to a fire hazard. It is important to follow the manufacturer's guidelines for proper installation of Romex cable.