There's one in my living room, and it's a new-build house (only 8-9 years old I think). I assumed it was there because of the gas fire? It does let out loads of heat as you can feel the cold draught from it. Ours is behind the TV cabinet, so we wedge a cushion up against it to block the air from getting in/out.
The extract fans in the bathrooms also let out loads of heat, and they should really have closable vents on them like these:
Maybe I should get some...