I work in hospitality and have noticed that lots of tables - typically 2/3 people - will sit for the entire meal with out talking at all and just staring at their phones! We took a booking for a lovely couple yesterday and they sat down and both got out a phone and looked at it until I brought the food over - they ate in silence - and then as soon as i cleared the plates they got out their phones again!
They were perfectly happy to chat to me when they ordered and I brought food but not to each other! (this even weirder as it was their anniversary)
Personally, for me going out for a nice meal has always been a social event where phones are only out to take a quick family photo/look up a question that we are discussing etc but definitely not for more than a moment or so
I just think that especially going out for a sit down meal I am paying for the food but also for the experience and the ambiance
so AIBU...
YABU - perfectly normal to spend a sit-down meal in silence/on phone
YANBU - wouldn't spend money on food out just to sit in silence