The advantage is that if other people do the same, the owner will be able to use others' data.
If you think "hey, the data is public, anybody can use it" - yes, but the fact that others are using it does not make it less of an advantage for the owner - it is still the same data.
Behave as if others would do the same. Maybe you publishing would trip somebody else to publish too?
I am glad Ivo did not ask himself "What are the advantages for me if I create a publicly accessible and free of charge windy.com?" when he started the project.