Since we haven't heard the airliner SAY they wanted an instrument
approach, how/why does the controller know to clear them for anything
other than the visual approach?

Use of an instrument approach simplifies establishing an arrival sequence.

So this choice is entirely up to the controller?

Seems like a giant pain for the flight crew, to have to keep all the various
approach plates, etc., at hand. (I'm assuming the commuter airlines we
usually hear don't have the sophisticated flight controllers on-board, with
all the pre-loaded approaches ready to be punched in at a moment's notice?)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"