Heat is the ultimate form of energy, any form of energy can be converted into heat but heat cannot be fully convert back. When a process produce heat which is not the processes main function this heat is generally a by product and so dissipated in the surrounding area.
To make use of waste heat can represent a huge economic gain for a company.
But sometimes, for little structures, the primary investment defeats the initiative. So, nowadays, in the context of climate change and energy transition, governments distribute subventions to help companies to contribute to a better energy use by recycling the heat in a rational way and not just throw it away.