I have worked in an environment where {maths degrees} really did seem to matter. An organization set up by people with {maths degrees} where other people with {maths degrees} seemed to have advantages in (a) getting in and (b) getting ahead. It wasn't ever really addressed explicitly (though "credentialism" was occasionally mentioned by others as well, I wasn't the only one who noticed). It definitely played zero role in my leaving that organization.

Maybe the problem is that maths degrees exist.