Very hard to make a business case because for the reasons you mentioned + the costs are very front-loaded because ontologies are so damn hard to build, even for very well-contained problems. Without a clear payoff, why bother
Yes because that is about formalizing all human thought and knowledge. In principle that has nothing to do with computers and is something everybody working in science and humanities has been always trying to do starting with Socrates or was it Pythagoras. It is about "building theories".
Now computers can help in that of course but it doesn't really make it easy to create a consistent stable "theory of everything". As we used to say "garbage in garbage out".
