I think the more fundamental reason most physicists working in the foundations of quantum mechanics don't believe in many-worlds is that those who do believe in many worlds consider the foundations problem to be solved, and see no need to work on it anymore.

Bravo. This potential for systematic bias on certain questions can be generalized and ought to have a name. It suggests that we should reduce the weight that we place on expert opinion on certain questions in any field, to the extent that the choice to work in the field will depend on how a person answers those questions.

So when we decide whether to rely on expert opinion, we ought to keep in mind that certain biases will tend to afflict precisely the experts, making non-experts in some cases more reliable guides.