I read somewhere it was used to prevent cupping of the lams lenghtwise in a tight recurve section of the limb. I guess for the hose to have a smooth surface to glide on.
I use glass that is sanded on two sides, not like the Botuff and BP so if I do not use them a slight pattern from the hose is visible after pressing.
Also if some dried glue spots is on a hose there will be a hard spot there that could press a bit harder than the rest of the hose. Such glue spots are difficult to cut off or remove.
Probably a good idea to wrap the hose in saran wrap.