I don't understand what the heat generated has to do with anything.

All electronic gadgets and gizmos emit heat. At least it's not a notebook that you can put on your lap.
I have yet to hear about a router that overheated and burst into flames, unlike some notebooks that did just that and caught fire (battery issue).

Heat will always be emitted by electronic items, especially PCs and their peripherals and accessories. But that does not impair their functionality nor is it a criteria for their viability as a purchase option.