Software security is a good example. Lets say you work for a large company, you have 50K repos in your git instance, and you have 10K developers on staff churning out all of that software from the mundane to the mission critical. You want to provide a means for your developers to be good citizens to get out in front of security vulnerabilities.

Building an in house solution to do this is extremely costly in every way imaginable, from the extreme expertise needed, to the ability to do it at a very large scale.

There are a number of vendors out there who provide great software to do things like scan source code, scan dependencies, or scan a live environment for vulnerabilities. The best of those vendors have cloud-only solutions.

You're stuck either accepting the risk that, at the very least, vulnerabilities about your software would be potentially exposed for the world to see, or installing an inferior product on-premise. That potential risk is even greater if your customers depend on you to store things like private and/or financial data.