Look around in any restaurant these days and you'll easily see half of the adults in the room engaged with their phones at some part of the evening, if not most of it.
The occasional check of your phone is very different than staring at your glowing rectangle through the entire dinner, ignoring those you are with entirely.
Like literally every human quality and habit, it's a spectrum, and people arbitrarily stake out a line on that spectrum (as we do with all the other spectrums).