[wyqydsyq]

Every tech company I've worked at used Linux for servers as well, however that doesn't mean I'm ignorant of the huge number of (predominantly large enterprise) corporations relying on the Windows Server stack. Also I would argue there are significantly more servers, embedded devices and especially networking infrastructure running *BSD than you give it credit for, not to mention every consumer device manufactured by Apple.

How many open source projects or tech companies can you cite using an SCM suite other than Git, except for Google which you already mentioned?

The huge disparity in usage makes it pretty clear Git is the only widely relevant SCM suite today. GitHub and GitLab are arguably the most active and central hubs of open source communities, and they're based on Git. Bitbucket discontinued Mercurial support a while ago. How many popular / impactful public code hosting repositories are primarily using SCMs other than Git? I'd be surprised if you can name a single one other than Google's now discontinued Google Code service.

[est31]

It depends on your success measure. There are way more Android users for example (most smartphone users), or people who interact with Linux servers (basically every person on the www), than people who use git (developers, a niche profession). The first two categories contain billions of humans, while the last category includes maybe a couple dozen million or so.