It is not done currently only because the energy use of bitcoin is so miniscule compared to other uses, that it's not even worthy to bother yet. Down the road, it'll likely change, but currently complaints about 'massive costs to the environment' are mostly virtue signalling.
Smart heating involves heat concentration, not heat production
"Smart heating" is just one more example of where Bitcoin in theory does not match Bitcoin in reality.
It is often considered more wasteful than those other things you listed because the mining algorithm is designed to be wasteful; i.e., if people design faster mining chips, it doesn't make anything more efficient or increase economic growth, it just causes the hashing difficulty to increase among all miners. That is sheer stupidity.
We probably disagree on what "tiny" means.