The average age of the last five memorial cup champions was approximately 19.5 years of age.
The average age of the last five NCAA champions is approximately 22 years of age. NHL champs over the last five seasons averaged about 27 yrs of age. (Quant Hockey Stats)
Based on the above, one could argue that there is no bigger determinative factor to success in the CHL and NCAA than elite skill and the age factor.
The level of growth each year at this stage of their development is substantial as evident by watching 19/20-year-old skill players play against 17/18-year-olds. (Knights vs Rangers last night).
The London Knights understand this better than most and I would guess so do most of the top ranked NCAA D1 programs. Why then try and recruit 18/19 yr olds CHL players when you could have them at 20. In addition, why would kids jeopardize losing an $80-$100,000 CHL school package by leaving early.
I believe there may be a scenario in the near future where the NCAA becomes the preeminent development path for North American NHL players, much the same way that most North American pro basketball and football players come through the NCAA.
Perhaps it's an increase in the number of D1 programs along with an increase in number of games played or simply the recognition that age and development is integral to long term success.