I tend to remove them because trailing commas break JSON. The similarities between JS and JSON are small enough for me to get confused over it and I'd rather remove the cause of potential errors there altogether.
There's a use case for everything. I for one am not wasting resources creating and maintaining two versions of fairly simple applications in a corporate BYO environment, like the one I'm working in. There are plenty of convenient and easy to use frameworks out there that make positioning and screen creation just as straight forward as Xcode or the android development tools.
Actually, I always find it a bit surprising Cordova doesn't have more competition.
Edit; I find the title misleading. It's not so much about Cordova as it is about hybrid app development