Also, a lot of not-for-profit entities intentionally branch out because such is the nature of helping the group of people they want to help. The term for it is intersectionality. That not-for-profits are heavily siloed is less a matter of intent and more a matter of history. If you are a food bank, you recognize that your intended client base needs food. But, second-order to that, why do they need to come to you? Is it because they need a job? Well, they're already here, so why not engage in skills enhancement and training? And since you'll be at the city council anyway doing advocacy for access to food, why not also advocate for more housing? If those continue to be siloed, you wind up with three separate groups, working at separate-but-related aims, each with their own overhead and inefficiencies.
It's vertical integration, in the not-for-profit advocacy space.