Because forestry is agriculture with trees as the crop. While USFS lands are often used by the public recreationally in the same way as parks, they have a fundamentally different purpose that aligns exactly with the different government departments they are part of.
Different agencies results in different responses to the same problems, for example, white nose syndrome affecting bats in caves.
The FAA does planes.
It's like - I'm guessing - the FCC got it because the first non-gov satellites were for comms. It's not likely the Luddites in Washington DC would have anticipated the situations we have today.
They also oversee the launch and reentry of space vehicles, amongst numerous other roles.
https://www.faa.gov/about/office_org/headquarters_offices/as...
I can't imagine that being an improvement on any axis ...