Timmies wants them because there's tremendous literal branding involved in the Tim Horton's logo festooned jerseys. They want them because there's tremendous emotional branding by being tied to the joys of sport. They want them because there are tremendous actual sales involved due in part to the name, and in part due to programs designed to get parents to take their kids to Tim Horton's after the game like their, "I just played, I'm thirsty" program that entitles Timbit uniform wearers to a free frozen lemonade or hot chocolate after the game.
And if you thought it was just hockey (70,000 kids!) and soccer they sponsored (like I once did), you'd be dead wrong.