The ITU has no enforcement power, but fundamentally that doesn't really matter much, since enforcement is handled by the member states. Are there attempts by various member states to skirt around the rules or favour their own national interests? Of course, and sometimes these are successful - but nobody just outright ignores the rules, because they know it very quickly leads to a tragedy of the commons.
Administering an orbital LVT is exactly the kind of thing that could slot cleanly into an expanded ITU mandate. Where the money goes would be up for debate, but I think the cleanest solution would be ITU rebates most of it back to the government of the country that applied for the orbital slot provided that they demonstrate it's going into a space sustainability fund.
Is it perfect? No, but it's based on a rickety-but-mostly-works international model and it doesn't require global government conspiracy theories to come to fruition.
Can't necessarily stop a multinational firing things to space on Russian/Chinese/ESA launch vehicles
It's like this bicycle meme where the person puts a stick in its wheels.
It's for the same reason that petrol cars are encouraged in the US.
Punishing SpaceX will lead to a bigger financial crisis, an upset Elon Musk who might refuse to fund the next democratic election and dozens of thousands of lost jobs (fortunately they already became millionaire, riding the right rocket) for a problem that most of the rich population doesn't care about.
Because in the city, it's about your petrol car, big trucks, and nobody to see the stars and a bit more pollution doesn't change much at that scale from their eyes.
CFCs (these gazes destroying ozone) were a notable exception, because it would lead to death of everyone (the same way that petrol with lead), except death, universally there was no advantage to defend.
But a space filled with US satellites is a great advantage for the US, since they are the only ones with the capabilities to deploy thousands of them, and it's a big business for military intelligence.
I can imagine the main reason they are going to regulate, is so that older satellite debris don't destroy the new shiny satellites, but beauty of the sky is going to be the very least important factor.