Intake Gasket Failure Question

My understanding is GM claims that the DexCool coolant is responsible for
intake Gasket Failures.
My understanding is also that the intake failures have been happening
since
around the mid 1990's. Isnt that before they even started using Dexcool?
If
I am wrong on that then I stand corrected. In any case if GM new that the
Dexcool was the problem then why didnt they just have a recall to drain
the
dexcool and refill all the cars with the green stuff? Would this be
because
GM would then be admitting to a known problem? The problem has been around
for 10 years unaddressed year after year. GM used to make some of may
favorite cars...Hotrod Chevelles, GTOs Camaros etc. But GM ....you done
changed. I just dont know if I still want to be your friend.