Because there is nothing in the design of the Boring Company that shows any significant or magnitude improvement over the existing ones. https://pedestrianobservations.com/2017/12/15/elon-musks-ide...

Throughout the centuries there were men who took first steps down new roads armed with nothing but their own vision. Their goals differed, but they all had this in common: that the step was first, the road new, the vision unborrowed, and the response they received — hatred. The great creators — the thinkers, the artists, the scientists, the inventors — stood alone against the men of their time. Every great new thought was opposed. Every great new invention was denounced. The first motor was considered foolish. The airplane was considered impossible. The power loom was considered vicious. Anesthesia was considered sinful. But the men of unborrowed vision went ahead. They fought, they suffered and they paid. But they won.