And whom pays for fixing it? Downtimes of self hosted systems using external software can be far longer. GitHub, unlike Amazon and friends, doesn't lie about their downtime. Every saas has hundreds of downtime instances across the board every month. Some are small enough you don't see them. Yet the services still work exceptionally well - and when they don't they get fixed in a quick manner. What takes them an hour would take most private orgs a day.