I agree on that question, but it's also a bit strange to say, because if you think about where BSD code ends up it's a pretty big market.

You have stuff where there is a big amount of FreeBSD code in it:

MacOS, iOS, Playstation 3/4, Cisco Routers, Juniper Routers, Android (though way less, then in the rest)

You have a couple of big names using FreeBSD in big amounts or for important parts of their infrastructure:

Facebook (WhatsApp), Netflix, NetApp, VMWare, Trivago, DuckDuckGo, Flightaware, ...

And you have big amounts of code in other projects. Stuff like OpenSSH and many libraries.

I didn't include the usual suspects, such as non router hardware manufacturers (ARM, Intel, HP, Dell, ...) that use it a lot, but they also use other stuff.

In other words: The market share I think grows if you use big companies. For smaller companies there is a rule of kind of sticking with the most used stuff. And that simply is Linux (among other things for that legal reason, already mentioned here).