I think it's a fair point; these bulbs are not used for heating because that's not their primary function (despite being more efficient at it than lighting). T

I think it's a fair point; these bulbs are not used for heating because that's not their primary function (despite being more efficient at it than lighting). The inverse would apply to, say, a fireplace. Light is an acceptable (even desired) side effect of the primary function, but it would not be convenient to rely on it for that side effect.