Because it's not actually a disadvantage, because if it's actually open source no one can stop anyone else from doing it. If you or your company wants to work 80 hour weeks to improve power efficiency on Linux, you can submit patches to all the different projects where nobody else is doing the work.

And that actually happens in real life. Most of the projects care to begin with because they use their own stuff and don't want to ruin their own battery life or have a competitive disadvantage over the alternative. Then other third parties that find business value in having it work pay someone to clean up the odd stragglers when one of them didn't do it or have the resources to do it themselves.

The main problem is when some vendor both doesn't do it and is hostile to anyone else doing it.