All services that serve Quebec have to be available in french. So if you're making an application front end, you have to provide a french version even if your userbase doesn't care. It's just extra overhead.
Well, localization is good practice and something that should be supported already. But I think it's more like the Quebecois language laws mandate bilingualism in the workplace, which is a greater hassle.
It's really that speaking french in a predominantly french region shouldn't stop you from getting a job you have every competencies to achieve. That's why the law can go into absurd territory(e.g. having only english equipment cannot be a valid reason to refuse employment to a francophone).
But then again, most of the law only applies once your business reach a certain number of employees(30 I think)