[throwawaylinux]

We could quibble about what exactly "primarily" means, but that's not the phrase he used which is "by, and for" without the qualifier. So here's two reasons to make FreeBSD for others as well:

- They use a lot of code that they don't develop. If FreeBSD is not for others then those external projects and developers would be disinclined to make their stuff work on FreeBSD.

- Every new FreeBSD developer comes from a non-FreeBSD developer who is interested in FreeBSD and probably uses it. More developers ~= better FreeBSD for FreeBSD developers.

- More users (very roughly) means more money. Whether that's money to pay for more FreeBSD developers, or incentive to make your hardware work with FreeBSD or port your software to it, there are some positive effects on the system and possibly your wallet.

- Personal satisfaction to develop software lots of people use. Also the recognition that comes with that can get you a job or help you meet people and go places.

So lots of reasons. Even being purely selfish and hoping to extract the most from it, there are plausible reasons why some amount of focus on others might be the best way to go about developing a the project.