I guess the reason why this option isn't on by default was bug #153204. However, I have just tried to reproduce it in compiz 0.9.7.8 and unity 5.12.0 with Firefox, Totem, and Vlc and it seems to me that this bug is gone. So, other than this current bug with unity, i don't think there is another reason not to make it default anymore.
I guess the reason why this option isn't on by default was bug #153204. However, I have just tried to reproduce it in compiz 0.9.7.8 and unity 5.12.0 with Firefox, Totem, and Vlc and it seems to me that this bug is gone. So, other than this current bug with unity, i don't think there is another reason not to make it default anymore.