The reason they're "not practical" is because the idiots in charge have let the fuel get out of control and are hamstrung by the very web of regulations that give them their power. The area residents simply don't want to pay for the risks they pose with their land management preferences.
Many are just too remote, and inaccessible, not to mention, if you did a controlled burn in these type of areas, and it gets out of control, you can't get the resources in to fight it.
Oh and it's IMPOSSIBLE for people to live there to manage it, right? The aboriginals did it for thousands of years. Nor is burning the only option; goats can handle awful terrain.
And even in areas that get burned, it grows back every single year.
According to Bonnicksen (who is the acknowledged authority on the topic of forest archaeology), there are a good many places where the Indians burned it nearly every year. Got a problem with that? I'll bet you do.
It would cost billions, and take an army of hundreds of thousands, all armed with weed eaters and machetes, and it would take them 20 years to do it.
And then when done, it would all grow back in a year or two.
LOL!