The point of the glamour prisms at all is to make a non-renewable regent that players will constantly want to have. By dividing them up via jobs, they ensure that each crafter is needed for a specific item which in turn increases the prisms value. I do agree that having the grades appear pointless though, but I understand why they exist which is again, to ensure that each prism has value. A rare Grade 3 prism (or something) is worth more than a Grade 1 or Grade 5 prism, which is sold at a dime a dozen.
Honestly in my opinion, the glamour prisms are the best items in this game for that reason. (Relatively inexpensive to make, can be sold at a profit and do not break the bank to obtain. Non-renewable so one always has to buy a new one, ect)
