Any Special Reason?

just the KGVI effigy, not common, and all Canadian Pennies are now being taken out of circulation.

Perhaps your interested in the value? Here's a link to a website that's a handy reference tool:
http://www.coinsandcanada.com/coins...nt-1937-1952

As for the reason for those specific years, it's near impossible to know although sometimes interesting stories can be heard from who you bought them from. In regards to larger circulated coin stashes however, it's very common for sellers to sort them into smaller groups based on year.

Another possibility, post-1947 they were chucked in a box which then got stored away for decades until the collectables were liquidated. Perhaps the original owner travelled to Canada and came home to the US with pocket change? If only they could tell their story It probably would be interesting. The center penny looks possibly uncirculated although it's red copper colour has turned brown with time and in that condition they are still quite common.