Yes, its not as simplistic as 'guests either go on rides or spend money in shops" and operators/designers do not try to "balance" those behaviours.
As Rappa points out, guest satisfaction / entertainment is still the core product, and for that there are definitely some good quantative metrics used by industry leaders that design or operate parks to ensure that the average visitors does enough "things" over the course of a visit to feel as though, at the end of the day they got their moneys worth (It varies by the type of park)
Guests that are being fed a good stream of entertainment will be happier and spend more, and linger longer and spend more. If they're not having fun they'll go home early.
Excessively short queues are only a problem insofar as that you might be over investing and spending too much running a park that doesn't need all that, but if a visitor is experiencing 1 hour waits per ride, you can definitely say they won't get enough entertainment in their visit and investment in capacity is warranted (Eg extra trains, new rides etc)
Edited just now by Gazza