Most business people are fundamentally interested in the good of the business. They require a college degree because they think someone with a college degree will do a better job.
Now there can be two reasons for that.
1. Skills learnt while getting the degree
2. The degree is a proxy for things not learnt during the degree. Think which things improve business value? General aptitude. Connections. Perseverance.
To the extent that 1 dominates, increased college attendance is great. To the extent that 2 dominates, increased college is an expensive signalling game.
Which is which? A little rule of thumb I have. If jobs require a degree from a good school, but the subject doesn't matter, then it's mostly signalling. If jobs require a particular degree, but the school doesn't matter as much then it's probably dominated by 1.
If interviews in the profession focus more on live demonstrating skills it's probably more 1. If interviews in the profession focus on telling a story that puts you in a good light it's probably 2.
How many people can a field absorb? Is it a fairly constant need of x carpenters are needed per capita to supply everyone with furniture (risks turning to signalling game about those fixed opportunities)? Or is it the more people we have, the cooler things we can build, the sky is the limit (clear this bar and your good to go)?
Is there a immigration of people in the field because domestic schools are not capable of meeting demand? That indicates a skill gap, 1. It can also mean the job is so shit no one wants to do it, but differentiating those cases should be simple.