But they do though. It might be significantly more expensive than GitLab and also only sold in packs of 10 user licenses and also not allowed to be run in a public-facing capacity. But they definitely do have a self-hosted option.
In fact I have been literally considering migrating our internal GoGS install to GitLab for the last week or two. The end of my day on Friday was downloading Gitlab and figuring out where to host an evaluation install.
Migrating my personal account over from Github to GitLab.com is a good chance to get some hands on time. Plus I can consolidate my personal CI setups at the same time, and I don't have to pay monthly for private repos.
Win-Win-Win.
PS: Always interested when your content comes up in my RSS reader. I do wish it was easier to share links without the unsafe content warning though. :P