It would be lovely to disconnect all together but some of us have loved ones (aging or sick parents, young children, etc) that we need to keep in touch with daily. And yes, I'm aware that they can EVENTUALLY get a message to us if there were to be an emergency but for some of us, an enjoyable vacation begins with peace of mind and knowing my kids can reach me if they should need to.
Just because some of us desire to stay in touch doesn't mean we're disconnected from our vacation of spend our meals with our "faces in phones". Everyone has different lives, needs, desires. That's why the internet is an OPTION.