It's funny. Reading a book among people, I do believe, was considered rude before the invention of phones or social media. It's still considered rude to take a phone call in the middle of a conversation, and when I was a kid, it was rude to text. Somehow, the latter changed in previous years. I suspect it may be in relation to how social media and technology drives our society. Businesses now use a chunk of their marketing on those platforms, so the social norm became new due to that need. Coupled with the fact we now can acquire many services from our phones, I think it looks more like a necessity tool to be present in any moment.

That said, I've definitely been around family who were all on their phones and I pulled out a book. When they say it's rude, I immediately fire back they're doing same thing digitally. Most times it ends up with both parties either putting down their distractions or moving on XD