Free Bus Rides; A Question

So, after taking the 53 and a few other routes over the past couple years, I have found it interesting that about once a week [[using the bus 3-6 days a week, depending on the weather) I do not have to pay for the bus. The driver just waives their hand over the toll box and says to get on, along with everyone else who gets on. This is of course, on the busiest line, and is often during peak times. What is going on?

If I do not buy a pass, and am just taking the single line, this saves me $153 a year. On a full bus of 52 passengers that is $8,112 a year that is lost on the 53 Route, assuming that bus is the only one not accepting fares [[number figured on a round trip, meaning it's actually happening twice a week).

The bus has been completely full before when this has happened.

What's going on?

Usually the fare box is broken when they do this... You would think that it would be worth it for them to fix it, but they don't. It happens on all of the bus routes all of the time... It really is ridiculous.

It's been a while since I have used the DDOT buses, but living in NYC has shown me how an essential an effective mass transit system is. In fact, I really don't like driving anymore. It's much nicer to sit down & pull out a book or something and not have to worry about some idiot on a cell phone broadsiding me.

I see there is a monthly "GoPass." I assume this is for buses only and does not cover transfers to the PM? I only assume this because it would make logical sense to have riders be able to purchase a monthly pass that would allow them to flow freely from bus to PM to the future Woodward light rail line, and logical sense traditionally has had little place in Detroit planning.