Who the hell mails stuff any more?
Can't speak for Canada, but this is what typical mail looks like in the US in 2014 (wife is a letter carrier of 26 years).
First class mail has dropped dramatically, but the PO still serves many purposes. In order....
Bills. Although I would venture the vast majority of users of this forum pay online, a great many people still receive their invoices in the mail. This is gradually decreasing every year, but it is a slow process. The older generations that have not used computers much, if at all, still do their business the old fashioned way. Many smaller companies (say, your dentist or HVAC guy, for example) still bill this way.
Magazines. Less popular in the digital era but still popular. I get
The Economist in printed format, never been a big fan of the digital version.
Parcels. This is a growth area for the PO and will be for the foreseeable future.
Direct Mail Advertising. The dreaded "junk mail". But is it? Consider: With direct mail advertising one can target very specific geographic and demographic regions. That is not possible with any other medium. If it was not effective, companies would not use it. If I ever opt to expand my side gig of home computer support my intent is to send first class (not bulk rate!) mail to the very best neighborhoods of Richmond (as they make the best clients). At 0.50 a letter, I can target 100 households for $50 and have a very good chance my advertisement will actually be read by the prospective client. I only need a success rate of perhaps 2-3% to make this worth my while. And with Zillow I don't even need to purchase mailing lists, I can get 100 desirable addresses in 1/2 hour of point and click.
For the big boys, mailing lists and bulk rate mail are standard fare.