There's a benefit to having multiple platforms on your development team if you are developing something for multiple platforms.

It's too often I see projects with "supports Linux, OSX, and Windows" only to find that none of the maintainers actually own a Mac and therefore it is filled with bugs and often requires the user to "find their own dependencies".

If we are talking days of time and not weeks, the benefits of making (and keeping) your whole system cross platform could pay off big time in the future when you or someone on your team wants to switch, or you just want to easily test on other platforms.

Exactly: Having a developer working on windows was a blessing since it allowed someone in the team to test on EI11 before we shipped to the product team, and it really improved our reactivity on this plateform. It wasn't our main target since our product was using webRtc(i.e. Firefox and Chrome), but it was supposed to fail gracefully on IE.

At least these days you can download VirtualBox images for free to test on IE11. But yeah, it's a luxury if there's a Windows developer that you can have fixing all the IE11 bugs ;).

I was under the impression that IE was standards compliant enough by version 11 that this shouldn't be necessary, but I guess not.

Well, it's pretty complaint to standards now. The problem is that it's just 2-3 year old standards.