Joining United MileagePlus is completely free, you just sign up.
About the same work as filling out a hotel wifi login.
About the same work as filling out a hotel wifi login.
But you need to give personal information which also has value.
At most they could see domains, ip addresses, timestamps, and http-only sites (are there any left?)
But the person sitting next to you can see everything.
Privacy filters are a thing.
they are essentially looking head on at it.
that may work for business class, but not economy.
privacy filters aren't magic.
You also give up your personal information when you step outside, take a bus, train, or drive a car.
Hell, even if you stay at home, you are giving up information for free that you are NOT outside.