And they should have the choice to go with cheaper electrical wire too? Get to choose what kind of materials to use for load bearing beams? No, building codes are not just for the owner/builder's benefit. There are community interests at play when someone is putting in a structure. Usually there are also lender interests at play; i.e. if the owner/builder defaults on the loan used to build, the bank wants to have something that is dependably going to sell.
Sure it can slow down innovation some, but this kind of oversight is definitely needed. Once that is admitted, it is just a discussion of where exactly to draw the line. There was a disagreement in those discussions, so a compromise was used. It gets reviewed regularly and the line can shift as needed when more information is available or the opinions in the disagreement change.