Guessing here, but the tall stacks will tend to bias the power curve to a lower RPM, so maybe the old A/FX cars needed more power down low, due to the clutches. Maybe when slipper clutches came along they were able to use the power in the upper ranges better, and the stacks go shorter? Sprint cars need the lower end grunt coming out of the corners, so that is probably why you still see the long tubes in use there.
I ran ram tubes on my Galaxie in 2008 and 2009 at Drag Week, and this year the guy who finished third in my class ran them on an SBC. So its not like nobody runs them, they just aren't as popular as they used to be. They are a lot more difficult to set up than a pair of carbs on a tunnel ram.