Comment by charcircuit

The work to do this isn't free. YouTube already has their code working, but they don't expect browsers to be blocking arbitrary requests or injecting their own javascript into the page. These kind of breakage are not free for YouTube to fix and often YouTube is the one taking the reputational hit for their site being broken. It ultimately is antisocial behavior to be breaking other's sites even if technically they can workaround the bugs being added.