I also realized something...
If there are banks that do not order $10 bills all the time, I wonder if they only order them during peak shopping periods (Easter, Christmas, and summer vacation/wedding season), and otherwise those banks rely on customer deposits for having $10 bills on hand? That may explain why the banks get far less crisp $10 bills per year now as opposed to 2010 or most of 2011.
I did notice that the number of $10 bills in circulation where I live has gone down - possibly quite a bit - since the fall of 2011. In 2010, I saw two $5 bills in my change about 80% of the time. Now it seems to be 95% of the time that I get two $5 bills in my change. Either the cashiers don't have $10's, or the number of $5's in their tills outnumbers the $10's greatly, despite the number of $5 bills in circulation across Canada is going down now.
I think the main reason why there were so many $10 bills in circulation before 1990 is more because of certain items such as certain clothing items/accessories, vinyl records, 8-track tapes, audio cassettes, and Super Loto tickets (the predecessor to Lotto 6/49) - the latter 4 of those items of which are now obsolete, thus pushing demand for the $10 bill in a deeper decline. Plus the $5 bill was continuously rising in demand at that time.
I remember watching a Game Show Network rerun of a 1989 episode of Sale of the Century recently (anyone remember that show?), and according to a question Jim Perry (the Canadian-born host) asked, I learned that compact discs outnumbered sales of vinyl records around that time. Compact discs have been demand for the $20 bill all this time, it seems. That kind of made me wonder if the $10 bill was starting to lose its purchasing power in the late 80's and not during the early 90's recession?