As a semantic architect, this is not my experience. In fact, I see very few large graphs in the wild. The problem is, unsurprisingly, that describing data is difficult. Relating your own conceptualization of a domain to anothers is frustrating and time consuming. It will always be easier to create a bespoke model. So, people just don't do it. As for OBO, there are many interesting comments here. The OBO ontologies all utilize BFO as an upper-level and in this regard they are united. But otherwise, their quality and utility varies tremendously. I still believe in this work and hope that one day everyone will think about their data as being longer-lived and more important than the software that generated it.