I used to work for a company that used on-prem BitBucket. And even there, "Stash is down" caused development to grind to a halt. Yeah, sure, our outages weren't synchronized with the rest of the world's outages, but the end result is the same: productivity depends on the uptime of our authoritative repo. That all the developers have clones of that repo on our own boxes is irrelevant... nobody's going to bother pointing our remotes at each other's workstations or reconfiguring Jenkins.

I’ve worked for a number of very large, enterprise companies. They use Github Enterprise.

Even banks are moving to SaaS first for their core applications.