Being able to self-host is a hard requirement for many organizations. Especially for tools like a wiki, which may contain proprietary/secret business information.

The last time we reviewed the Atlassian Cloud hosted products, they did not meet our security needs (requirements include isolated tenant from other customers, customer managed keys, etc) though they were much closer than a few years earlier. We also review the general security practices of the company (for example to make sure they implement a secure SDLC and follow other security best-practices).

Plenty of deployments will continue to be on-prem, cloud is not perfect for 100% of use cases.

Example: If you are a semiconductor manufacturer, you probably are not going to be storing all the documentation about your bleeding edge fabs on a cloud provider.

PII, PHI, classified data, controlled unclassified information, proprietary trade secrets, a requirement to host user data in the country the user lives, a company is massive enough to own data centers and may as well use them. There are so many reasons to self-host. Unless your service is as big as AWS/Azure and can afford to build a private cloud in a location of the customer's choosing for sufficiently large customers, "only cloud" isn't good enough for many use cases. You're putting your own convenience as a developer ahead of the needs of certain users. Which is fine, I guess. You don't need to serve everyone. But you shouldn't be out there acting like self-hosting never makes sense. You may as well ask why some facilities have their own generators and their own wells and don't just universally hook into the public grids. Some applications have requirements for hard perimeters and self-reliance.

The issue is that to put company data on your server, we need IT security people to sign off on it. That takes years and a lot of budget, just to get that authorization. It also likely comes with restrictions, like not being able to use it for very sensitive company data or government data.

In short, that’s not happening for a wiki.

>I'm not sure there is any commercial knowledge base tool that are available on-prem.

XWiki?