Why does everyone develop on mac and not a cloud IDE?

I have noticed while going through hundreds of tutorials of web development that all but, I can literally only remember 3 tutorials not for mac, a few tutorials are for mac and osx. Why not develop on the same platform you are going to launch your application.

I work on c9.io but there are also nitrous.io, Koding.io, and I thinka few others. These run on ubuntu 14.04 and do update to newer ones as well. I am still new to this, about a year, but it seems odd that all these developers develop on a platform they will not launch on. Or am I missing something.