If we must trot out the old car analogy trope, let's at least be realistic.
If the iPad were a car, you'd only be able to install car radios approved by Apple, of which there would be forty or so wildly different options, some of which generally sucked, some of which were meticulously built around a particular set of stations, and some of which you could tune to anything from low-frequency maritime navigation channels to shortwave.
Or you could just take out the radio and install a talking river trout in its place, so long as it was available in the aftermarket catalog.
Yes, except you wouldn't be able to play your favorite Indy radio because Jobs is just not into Indy. And no amount of complaining will ever get you that radio.
It surprises me how quickly people forget that there's no Opera Mini, no multitasking, no Google Voice, or a myriad other applications that are arguably far, far more innovative than anything that's in the App Store yet you can't access them because The Man told you so. Especially since those are some of the things that make a smartphone so useful.
But Apple would never let me install a radio that would tune into adult shows like Howard Stern. And they'd block all Sirius XM radios because of this possibility.
And if someone created a radio that used too much battery life, I wouldn't be able to install it either.