This has been my experience too. I think of Github as more like a social media platform that incorporates git as a convenient feature. Large corps use it as a marketing/PR forum and regular people use it to connect to other people interested in programming.
But what software are large corps use then? I work at a fairly large coorp (>650000 employees) and they are indeed using Github Enterprise (and some other solutions like Bitbucket data center). I'm would be quite surprised if they really only use software like Github for public things.
Azure DevOps is in a weird zombie state where everyone knows Github is getting all the development attention (and presumably most of the workforce now) but Microsoft is keeping it on just enough life support to keep companies "happy enough" and are still refusing to call it "dead". (They continue to point to the development roadmap, which is still actively maintained, but to some like me read very much like "bare minimum maintenance feature set". It also doesn't help that of the few open repositories for checking in on AzDO development, such as their community proposals repo, which are themselves hosted on Github, hah, it is very transparent most haven't seen active commits since 2019 or 2020.)
Bitbucket has a lot of Jira-integration and a lot of large corps are in Jira for the long haul now and "might as well get the synergy of Bitbucket".
Plus, don't underestimate the sunk cost fallacy factor keeping a lot of large corporations locked into things like Perforce and ClearCase.
With my last four employers, two used subversion, one used git (just git -- not github or the like) and my current one uses whatever Azure Devops is using.
I made a filter list for uBlock Origin (and compatible) ad-blockers that can hide many of the social media aspects of Microsoft GitHub to make it a bit more tolerable when forced to interact with it due to project lock-in.
