Why should they, though? He seems to be staking much of his credibility on vague accusations that someone is not doing the work. Mostly the case seems to be that his propositions are not being ignored, they simply lack substance.
The thing is, the less evidence you have, the easier it is to come up with any number of stories that "fit" the data points. Historians therefore need to be extremely conscious about only drawing conclusions that have an undisputed record supporting them. That is the whole basis of the scientific methodology; if you can't get the evidence, you have no argument.
The period Hancock has chosen to focus on is commonly called "prehistory" for a good reason, as without any written records, there's not much of a basis to build any kind of narrative that stands up to scrutiny. Especially if you only cherry-pick data points that fit your assumptions, and wilfully ignore a gigantic void in the rest of the known record.
Surely that is a problem with the credibility of the claims themselves, and not the rest of the world.