You're arguing that shaving off a couple minutes a day is worth the loss of human dignity that these workers experience.
And when we talk huge sums of money, morality often is tossed out of the window first.
I don't really see it that way. In my view, small businesses abuse their employees just dramatically more than large businesses.
For a small business, a single employee may be the only person working the till. The employee simply won't be allowed to go to the bathroom at all except during designated times.