[Nextgrid]

A lot of large web services outages (such as GitHub, Azure Active Directory, Slack, etc) are purely caused by these services having to scale to the entire world, with all the complexity and moving parts it entails.

Self-hosting inherently mitigates that problem because you now need to support less than 0.1% of the load of the worldwide service.

It also puts you in control of maintenance and updates - you can choose to make changes outside of business hours so that nobody is affected if you screw up. Developers at SaaS services can't easily do that because it's always business hours in some parts of the world, and may not be motivated to do it anyway even if it was possible with some effort.