I think there was a discussion on this a while back,
I was thinking about it,,about the best example I could think of is when you have a piece of wood or stave that will not make a bow,,,
say a belly split thats has a violated back and not enough wood to get to one ring,,,so useless as a self bow,,or any bow,,
with a sinew back it can become a hard hitting deer killer,, then its worth the effort,, I could go on,,but that seems to be one of the best examples in my mind of when sinew is really a great way to make a bow,,
I use it on shorter bows,, cause I like the way its holds a profile,, and the performance,, but really nice short bows can be made without,,I just like the way they shoot,,,