You are missing nothing Art, in fact you will find unswitched power behind the dash, check out a Bentley if you don't want to run a wire.  The only thing you are missing is the number of times you are going to need to jump your car in the following year before you truely learn to turn off the radio.  Not being funny, it will happen, be prepared.  Otherwise a fine idea.
John Anderson

________________________________

From: Art awa0330@GMAIL.COM

my radio in my '86 Vanagon Westy.  I plan on wiring it
directly to the battery so that it will operate without the ignition or key
in the slot. Isn't this simpler, except for the obvious downside, which is
that I'll need to remember to actually turn on and off the radio by
depressing the on/off button? Am I missing something?

Art