Suitable Line Weights

I just finished reading the Lyon's reprint of J. Edson Leonard's book
"Feather in the Breeze". Leonard was a fisherman who started
flyfishing, mostly in the East, in the 1920s. In his chapter "The Long
and the Short Of It", he refers to one of his favorite bigger river
trout rods as being a 9 1/2' Phillipson cane that threw a DT8F(!)
line. He claimed that it would "place a dryfly as softly as a thistle
dropped by an upstream gust". Interesting.

My question is, other than the pleasure of experiencing the lightness
in the hand of the rod itself, do you think it is really necessary for
people to use very light lines to be able to catch trout? I know that
my first three seasons on Black Earth Creek ( a southern Wisconsin
spring creek) were fished with a 6 wt. line and I caught fish (2000+
according to my old logs) on every thing from a #6 Hex dry to a #24
midge with no more spooking of fish than I do now with my 4 wt. rods.

g.c.