For courses in cold northern climates, fast drainage means the soils get warm faster in the spring, which assists with growth. Somewhere I recall reading it takes 500% more energy to warm wet than dry soils.
Herr Ristola, that is a correct figure you state. It's a very important and oft overlooked factor of turf needs. Put another way, but saying the same thing . . .
it takes 5 times longer to warm wet soil as it does to warm dry soil. Thus, as you say, the growing season (Golfing season !!!) is shortened. Wet soils results in less revenue, access, level of enjoyment, etc., and with more issues of soil bourne diseases and
poa annua infestation, etc, and reduces the possibilty that a course will be designed with fast & firm conditions. Which, of course, brings us back to the level of enjoyment.
Another process of importance is that absorbtion and transport of water and nutrients are inhibited by low soil temps, thus compounding lingering problems. Bottom line . . . wet soils suck long term. (Isn't that a quote from Full Metal Jacket ?)