The lavatory sink is potentially infected with pathogens from somebody's mouth...they got there through a cough which someone cupped in their hand and then used that hand to turn on the faucet.

You walk in next and touch that faucet a few minutes later.

In the case of pillows and blankets, first, I am skeptical of your assertion that people rest their mouths on these.

Have you seen someone using an airplane pillow on their mouth? When? During a failed mafia hit?

But let's assume you're right for argument's sake.

By the time you get on the plane and use that pillow and blanket the time period elapsed has been far longer and most pathogens will no longer be active by then.

And even if they are still active, using the principle you stated earlier, as long as the pillow and blankets don't touch one of your orifices and they're not touching broken skin, your likelihood of contamination is virtually nil.

Head lice, yes, but as I wrote in an earlier post, there is no reason why head lice wouldn't also be present on the seat back.

The greatest health hazard on a plane is the person sitting next to you. It's a very confined environment and if that person is very sick and constantly coughing a few inches from your face, your likelihood of contamination is high.

And there is essentially nothing you can about it.