Im not sure it really has to be a whole conspiracy; companies won’t pay someone a lot just because people think that that person ought to be paid a lot, they’ll pay someone as little as they can while still getting the people they need to fill the role. Having more people with a given degree can even drive the wage down for that position by itself if the number is above the number of available jobs in that field, so having people value those degrees less and become less likely to get them would ultimately serve to make them rarer and therefore drive required wages up. I think a simpler explanation for people being dismissive of college degrees is a combination of them being more common, and that those without one have a desire to not feel like someone that does have one is smarter than them in some way, and an easy way to avoid such feelings is to convince oneself that the degree is meaningless.