I don't get why people use 1.1.1.1 8.8.8.8 etc, for more then debugging. Why tell Google et.al about every site you visit !? And get slightly slower, less accurate and less resilient DNS lookups ...
And because most site visits start with a Google search anyway.
And finally, because I am comfortable with their privacy statement : https://developers.google.com/speed/public-dns/privacy
it's not that slower.