Who said anything about a problem? I thought it was entertaining, and I'm hoping we can do it again.
There's no in-universe explanation for it. It was likely either a developer oversight, or they just didn't care enough to factor the radio into the stealth mechanics.
They could, but it's more of a question of whether or not they would find it worth the time and resources it would take to program complex stealth game algorithms into the AI. I'm sure they could do it if they wanted to, but since they make RPGs nuanced stealth game AI like that isn't going to be as big of a priority for them as it was for the developers of games like Thief: The Dark Project and Metal Gear Solid where stealth is the actual focus.
In a perfect world Bethesda would be able to put as much time and resources into perfecting the stealth gameplay as possible, but I'm not sure how feasible this actually is in reality given the size of their games, and how many different systems they have to juggle. This is why I don't think we'll see foresee any drastic improvements. I can't see the future though, so who knows.
Did it? I thought it was the same thing in Oblivion and Skyrim that it has been since Daggerfall. TES and Fallout stealth is mostly just number crunching as far as I can tell - with the games constantly determining your visibility to AI based on your character's sneak skill level, and perhaps a virtual roll of the dice. I wasn't aware there was anything else factoring into the mechanics. Not saying I don't believe you, I just haven't looked into the stealth mechanics in any real detail - I only have my limited experience actually using them, so I'm curious as to what these differences actually are.