That's because college-as-increasing-earnings-potential is the simplest way to rationalise taking on a lifetime of debt.
Spending $100,000 to boost your income by $20,000 per year for life is a very simple argument.
On the other hand, to argue a manual labourer with a $100,000 philosophy degree that didn't boost their income at all had nonetheless made a good investment requires much more complex arguments about the nature of human happiness and the inherent value of knowledge to the individual and society. Which in turn leads to a wealth of follow-on questions which can't be answered with any finality.
Consider knowledge as a strict tradeoff against things like interesting vacations and buying a house N years earlier, and it's genuinely tricky. Would you trade buying a house at 30 with less knowledge of liberal arts for buying a house at 40 and knowing a BS worth of liberal arts?
Luckily (unluckily) the decision is easier because to buy a house at 30, you likely need the degree too, so the question is flipped.
Philosophy majors are about the only humanities major with a marketable skill: actual skills in critical thinking and not largely an illusion of critical thinking
As such they do better financially than other humanities majors:
Spending $100,000 to boost your income by $20,000 per year for life is a very simple argument.
On the other hand, to argue a manual labourer with a $100,000 philosophy degree that didn't boost their income at all had nonetheless made a good investment requires much more complex arguments about the nature of human happiness and the inherent value of knowledge to the individual and society. Which in turn leads to a wealth of follow-on questions which can't be answered with any finality.