I was a bit shocked when in some Canada's Horton's there was a disposable needle trash for the junkies, so I get why WiFi might be free for all but restrooms not so much
Pretty much the only times I'll go into a Tim Hortons is when taking a break on a long drive. There's a lot of highway out there where Timmy Ho's will be your only option, especially at night, so it's not surprising to see the drop boxes. Proper rest stops have them too.