Yeah but you can challenge a patent without even going to court. If your reasoning is compelling enough a simple request for re-examination will suffice. The problem is that these corporate giants DON’T have a compelling reason to challenge the validity of a patent aside from the desire to either acquire it themselves or avoid licensing its use.
If a patent truely was over-reaching or stifling innovation and progress the USPTO would be required to remove it upon re-examination. The problem is that the patents in question typically required millions of dollars in research and the USPTO is not in the mood to take that away from companies on a dime.