Except: editing is done by an unruly hive. There is no organizational nexus on which to place "comply or we'll withdraw our advertising" pressure. And, any attempt to apply such pressure would quickly trigger its own self-nullification via editor outrage (as with the 'Streisand Effect').

In order for an advertiser to have sinister influence, you'd need to assume a bunch of other changes which weaken Wikipedia's resilience. Advertising could be implemented in a way that helps prevent such weakening-changes from happening. And if any org could pull that off, Wikipedia could.

That said, I still understand why, given their community's biases and their success with donation-drives so far, they have not seriously considered ads in many years. Don't mess with what works is usually a good principle.