why settle for second best? The RIGHT answer is acheivable just as quickly as the "best guesstimate"?
Back when I flew single-seat fighters with round dials, it was often "too hard" to dig out the whiz wheel. Besides, they taught us the rule of thumb in flight school, so it must have been "good enough"...
Of course, 30 years ago I didn't have GPS, FMS, INS, or any of those goodies...