"Remove abandoned wiring" is just one of those things that simply can't be addressed with a simple code change. Let me use a certain restaurant job to illustrate the point ...
This restaurant wanted to have "cable TV." Oddly enough, so did the last several owners of the restaurant.
Each time, the cable / satellite provider brought in his line, installed his dish, ran his cable across the rooftop. No matter that there were already several dishes installed; a new one got mounted.
Simply put, the guy was hired to bring in TV. He was not hired to remove the previous installs. "Ethics" and liability issues would discourage any attempts to use the previously installed equipment. It simply is not the responsibility of the new guy to remove the work of the previous guy.
Nor would this sort of thing ever get inspected. Even if it did, the inspector does not have the authority to tell the contractor to remove the other guys' work.
Multiply this by the multitude of phone, data, alarm, CCTV, sensor, sound system, etc., wires that folks string through theeir places. With technology changing every few years, you're guaranteed quite an assortment of cables.
Fact is, there's no telling what's in the walls without tearing the place apart. That's just not going to happen. It's not the sort of situation that lends itself to solution by regulation.
So, where is the solution? There really cannot be one, unless something changes that will make it to someones' advantage to remove the old cables.
An example of such an 'advantage' is the zeal with which old plumbing and power wiring is removed- with each increase in scrap prices. Another example is the way certain insulations are replaced with better ones, as heating bills increase.
