They simply aren't doing so.
And they continue to hide behind the worn out excuse that the status quo is "what we hams want". What they interpret, as "what most hams want" is what the ARRL tells them "most hams want", even though the League's membership has never been more than about 25% of all licensed US hams.
But, even so, if I had perpetuated such "half-baked" excuses as the sole reason for non-compliance with the rest of the Federal Code at any time during my 20 years as a US Government comptroller professional, I would have been fired on the spot. In my estimation, such bureaucratic laziness now goes well beyond simple regulatory malfeasance to the point of being blatant, benign neglect of a duly authorized radio service.
Any way you cut it, that's criminal.
This becomes particularly true when the FCC could very quickly (and, I believe, very easily) get rid of a huge part of the blatant systemic discrimination in our licensing system and all without changing anyone's license class or reissuing anyone's license.
In fact, if they really wanted to, they could do it all with just a simple stoke of a pen.
All the FCC would need to do is simply remove all the artificially regulated sub-bands (and sub-sub bands) on HF and then grant anyone holding a General, Advanced or Extra Class license identical operating privileges. At the same time, anyone could apply for any available call sign under their so-called "vanity" call sign system. It would be "first come, first served". Which is as it should be anyway.
This would also allow all of our bands to revert back to their underlying ITU maximum emission bandwidth criteria, which is, as I've said, the way most other countries in the world (like Canada) already do it.
What's more, under this scenario, nobody would "lose" their current operating privileges. In fact, this approach would (finally) recognize the fact that there IS virtually no operational difference between the operating privileges now granted to a General Class licensee and those of Advanced and Extra Class licensee in our Service in the USA today.
And, of course, this would also mean that it would once again be left up to we hams to decide "what goes where" on our HF bands, just like we now do on our VHF and above bands. This is something we have, by the way, already been doing…. for decades. And that "sky" has yet to fall.
The only thing the remaining Advanced and Extra class license holders would now have under this new system would be "bragging rights", which, from a legal and regulatory standpoint, are largely irrelevant anyway. That is, of course, irrelevant except in the elitist minds of that ever-shrinking minority who have been using their Advanced and Extra Class licenses as US Government permission to look down their upturned noses at everyone else in our hobby. Under this new plan, all of that snobbery would now lose its US Government sanctioned underpinnings.
But, operationally, all three licenses...General, Advanced and Extra Class...would now become virtually identical…which, in reality, is what they already are.