Don't they, though.
I have come up with a Natural Law of Organizations:
All organizations (for-profit, non-profit, government) come to the same bad end, which is serving the organization itself, rather than whatever mission they started out to serve.
This includes internal struggles over organizational money and power, as well as doing whatever it takes (mostly ka-ching) to maintain and expand the organization. Sometimes these behaviors are framed as efforts to serve the mission, but...not really.
Because this evolution happens naturally, the only way to prevent it is with a dedicated, ongoing effort. This rarely happens. Most people are oblivious to it. Those who are not, don't necessarily know what to do about it. And some of those who do, prefer to take advantage of it, rather than prevent it.
There has been a further evolution with internet, as more and more organizations exist mostly or solely as websites. Their actual mission is almost invariably ka-ching through data mining, and they seem to stay true to it. Otherwise, they don't even devolve from serving the stated mission to serving the organization. They choose a stated mission that they think will serve the organization, by attracting a lot of people to sign up/share their data.