Sometimes when a high-profile startup is acquired for a premium, its competitors are also acquired. With the acquisition of GitHub by Microsoft, who will rush to acquire GitLab?
They already have both a version control and a continuous integration offering. So, it wouldn't really make sense for them to buy GitLab from a products point of view.
Maybe because unlike Google, Yahoo, Facebook etc. many HNers are forced to use this software at work. Other than that it's just another quirky but useful bit of bloatware.