What an inspection is really looking for
Live bugs are the last thing you find, not the first. The earlier signs are dark spotting along the piping and seams, shed skins tucked into corner folds, and a sweet musty smell in a room that has been shut up.
A light encasement changes the arithmetic. Spotting shows against white fabric, and the seams a bug would otherwise hide in are sealed underneath the cover. A housekeeper sees a problem during a normal strip instead of during an infestation.
That is the practical case for encasing an entire property rather than reacting room by room. One encased bed is a protected asset. An encased floor is an early warning system.