I think the key word is “always.” It is probably true that an average humanities graduate earns less than an average mathematics graduate (I chose this instead

I think the key word is “always.” It is probably true that an average humanities graduate earns less than an average mathematics graduate (I chose this instead of engineering where there might be professional qualifications involved). However it is less clear that an average law or mba graduate would earn less than an average mmath graduate. And for those degrees an undergraduate in humanities is required so surely that degree must be considered worthwhile. There are also good government jobs which are full of people with humanities degrees, and plenty of people with mathematics degrees which they gain little from. I suppose the point I want to make is that if American universities all stopped offering courses in the humanities then there would likely be complaints from government departments or industry about not being able to find sufficiently educated candidates. I suspect that if half of universities stopped offering those courses the effect would be much smaller.