Answer: BECAUSE!
Seriously though:
Linksys in their vast wisdom constructed the built in camera firmware to interface with a streaming video format ASFPLAYER. This format requires an ActiveX program in order to display in a browser window.
Micro$oft in their wisdom constructed ActiveX as a pseudo proprietary component of it's windows products including of course Internet Explorer.
Mozilla / Firefox: in their cocky wisdom decided they refused to even consider mucking with the M$oft proprietary ActiveX requirements and there is apparently no interest in doing so in the future.
So what is the answer to this conundrum. Well, if you really just absolutely must see my webcam and let's face it, it's the most incredible webcam on the internet, then you need to fire up your Internet Explorer program. Now be honest, you do have IE installed don't you?
Having said that, the Linksys wireless internet camera serves its purpose quite well once you figure out all of it's quirkly intricacies.
So, hope you take a look using IE.
Brian.