Probably because the accusation isn't true.
It takes much fuel to cremate a human than you get by burning it. IOW, the burning of the bodies is just not a source of heat.
My first reaction. I'm surprised it took til your post with this tech savvy group.
What accusation? Ten of the NHS Trusts admit to burning aborted and still birth "along with other rubbish". And two admit to using same for "waste to energy incinerators"
Are you wandering down some side street?
Your first and third statements are demonstrably false. (Your second statement is a little garbled - did you mean to say that it takes more fuel? - so I won't comment upon it.)
The combustion of human remains is without question exothermic, i.e., it yields a net plus of calories (energy).
To be sure, some initial input of energy is necessary to get the process started - and, in fact, because of the high water content of human bodies, the process may not even be self-sustaining (depending upon how well-designed the combustion chamber is; as little heat as possible should be allowed to escape through the chimney - rather, the flue should be equipped for heat recovery, this recovered heat then being returned to the combustion chamber), but it still has a net energy yield.
Consider: Carnivores eat animal cadavers, and "burn" them in their digestive tracts (in a very inefficient process that doesn't even yield ash as a final product, but rather feces which themselves still have a relatively high caloric content) - yet still don't starve, which they would if it were an endothermic ("energy-consuming") reaction.
Regards,