Ask HN: Why is evryone making Chrome extensions without a Firfox counterpart?

Most likely because they're scratching an itch and don't happen to use Firefox.

This is similar to why a lot of projects on Github don't support Windows despite the market share of Windows being much bigger than that of both Linux and OS X put together. Among the demographic Joe Randomdeveloper cares about — himself — Chrome on OS X has 100% market share.

I think the major reason is that the marketshare has changed. Chrome is now at about 2x the marketshare of Firefox.

Source: 1. http://en.wikipedia.org/wiki/Usage_share_of_web_browsers#Sum... 2. a German computer magazine called "c't" - latest edition

Because NaCl. It's basically Google's version of ActiveX, not supported by other browsers.

http://en.wikipedia.org/wiki/Google_Native_Client

I wouldn't say NaCl is the main reason. Devs just develop for chrome because they use chrome themselves...