See what I was saying? Strange crystals lying in towers distributing vocations is no basis for a system of employment. What you do in life should be decided by you and you alone, not from some farcical crystalline ceremony.
Why on earth would some random crystal doodad know what you should be doing better than you?
The Orb is basically a substitution of the Status Window that is common in games and in many Series (Isekai or not).
No one has ever questioned why the Status Window showed the Class/Job of a character or assigned Level/Rank to them and even how much proficiency (or limit to it) they can have in it. Nor has anyone question why they shouldn't be forced to follow it.
Also, the Orb isn't
distributing Vocations.
It's informing what you are best at by reading your specs (like a Mind Reader or Fortune Teller is supposed to do), and it's also doing it based on a Ranking System, meaning it's not just focusing on one trait, but giving you a list of things you are good at, and ranking them.
As for the last part, it is always said that a person can't themselves judge their own skills or talent, but need an outside perspective to know what they are good or bad at.
This is what gave rise to the concept of Teaching, as Teachers are meant to teach people and then see what they are good at and help them grow with the one they are better at (though its something that isn't followed in modern education system).