Just cuz birds do not have feathers on their feet does not mean their feet are at great risk from cold, nor does it mean their feet are a major source of heat loss.
The way that blood vessels are routed through the legs and feet of birds makes a countercurrent heat exchange system, so that most body heat stays *in* the body rather than the feet acting as a radiator that lets lots of heat escape to the environment. If you notice, wild birds have bare feet and legs and yet species that are generally adapted to cooler environments do just fine with those bare feet and legs. Ducks and geese will stand on icy ponds and neither get frostbite nor melt holes in the ice from their body heat
Parrots are simply not adapted for temperatures below "warm weather". Many are not, uh, the very hardiest birds in captivity either, at least not compared to yer basic chicken. In cool situations (including things like 'having the air conditioner on near the parrot cage
) parrots need
all the help they can get. Thus, heated perches.
Chickens, OTOH, are quite cold hardy. They are not, not even remotely, parrots
A quick google did not find any heated parrot perches for sale that were larger than 2" diameter anyhow (and remember that is *round*, not flat on top like chickens usually prefer), thus not really well suited for chickens anyhow.
JMHO,
Pat