And then it can't use that money on its mission because it shut down.

> Isn't that a part of their job?

No, it isn't. Their job would be to use the income that they received from that part of the business and spend it on their mission.

There are all sorts of non profits that operate in a similar way.

In fact acting sustainably is generally a positive for non-profits because it means that you can be more effective for longer without having to rely on donations.