Shouldn't this type of thing be global? Why per style?
This flexibility is
good. It allows you for example to create different versions of the same style, for different holidays. This way you can quickly switch to a Christmas, New Year, Halloween logo...
Example:
- your main style with normal logo (parent style)
-- same style with Christmas logo (child style)
-- same style with Halloween logo (child style)
- other style (sibling style)
-- child style of sibling
But you can even use a global logo for all styles:
- your main style with global logo (parent style)
-- other style but with the same logo (child style)
-- and another style with the same logo (child style)
So you see the possibilities are endless, whereas they would have been very limited in case of one global setting.