I would say, as others have, remember that you are seeing a few moments out of someone's life and unless you think someone is in some kind of danger, it's not your business.
I take my 16yo DS out to lunch in a restaurant about once a week. If you saw us you would likely be very judgmental, as I can feel some people around me are. We are both eating sitting looking at our phones on the table in front of us (me reading a book on Kindle, him most likely watching YouTube clips about the Ukranian war, or alternatively about other people playing Roblox games).
So:, this is what is really happening: He is autistic and non-speaking, and the way he talks is by typing into a text-to-speech app on his phone. So if he wants to talk to me he has to put down his knife and fork, lose his concentration on his food and type out what he wants to say. Given that he likes pontificating at great length about things he is interested in, this would probably mean his food gets cold and he never actually finishes it. And if he just had to sit there not watching something he would very quickly get bored and restless and start disturbing other people.
So we have agreed he doesn't talk while eating unless it's something urgent. I dont feel it is right for me to just talk at him when he can't reply, so we eat in companionable silence while enjoying reading or watching what we want to. When we get back in the car we chat all the way home.
If you judged me negatively by just what you saw in the restaurant you would be dead wrong.
Not saying that the situation here is necessarily anything comparable, but I would ask people not to be so judgemental when observing a few isolated minutes of a person's life.