Sounds good. If you’re squeaky, but cut off the high end and boost the bottom you sound less obnoxious.
There’s also the point that the low end tends to survive static noise better than treble, so they also boost the bass to up the intelligibility of the radio signal.
Or, more accurately, the mix is done by people who get to listen on studio monitors in a studio. So they make a lot of choices based on a nearly completely silent environment, and with knowledge of how the radio signals work, but likely don’t listen to the actual radio in their car much anymore.
Also, radio studios almost always use a cardioid dynamic mic, which increases bass response the closer you get to the mic. And nearly everyone I’ve seen on-air is eating the mic.