Also, that sheet of paper is valuable to employers. It verifies that you know what you claim to know. Sure, you could know all that a school teaches you, but if I were an employer, I’d like to have that confirmed somehow. That sheet of paper is a great confirmation.

Of course, there are many things that one needs to know in most occupations that cannot be learned at school.

A “certificate” of educational acheivement is helpful if the position is in management, financial, personnel or business organization. The irony here admittedly is that no one at my company except me has come close to having a “certificate” to justify thier postion. Which brings me to the next point…
Experience. On the job training or learning on there own on the job.
The is something to be said for that. However, getting them to adapt to the way you do things first can be challenging because they have to overcome some possible bad habits first. That is what comes from on the job training or learning on your own how to “play or work the system.”
I’m not poo pooing education here. It is an excellent springboard into the field one wants to get into. That piece of paper you worked and spent hard for is worth something to the potential employer. It is thier “security blanket” in a way, that you do know what you are talking about, or they hope you do and that blanket helps them feel better about the chance they are taking in hiring you.
I am contemplating starting my own business. I have two possibles in mind.
One is a retail idea that, when interviewing potential employees, I would weigh heavily thier passion and interest in the subject.
The other business would require some positions to be certified in it because of my affiliation with a supplier who would require it and I would want someone in that position to not only be certified as required by the supplier, but I would also require that that person would have the passion for the position and understanding of my passion as well.
So, as an employer or potential employer, what I would look for is both objective and subjective when weighing the risk I would take in hiring personnel.
A footnote:
Usually when we have had applicants come in for an opening and they talk too much about how “damn good” they are, especially welders, the test is in thier performance on the welding test, and they are more times than not, so “damn bad” at welding. Or they are so damn bad at working as a team/company member.
If the energy they spent on thier mouth was better invested in thier performance, they would do so much better. Certified or not.