Do restaurants need to post "No phone" signs?

We went out for dinner last night to celebrate an anniversary with our daughter and son-in-law at Houlihan's in the Kingsdale shopping center.  We had expected it to be crowded because it was a home game day, but were pleasantly surprised that at 5 p.m. there was no problem with service. I was wearing my new scarlet and gray outfit (OSU colors) which was a birthday gift.   I had a very lovely meal of petite filet mignon, grilled asparagus, garlic green beans, wine and a tasty salad. Near the end of our meal I noticed a beautiful young couple come in--they may have been dressed for Arlington's homecoming--the short swingy formal dresses are so popular. Within a minute of sitting, she whipped out her cell phone and began scrolling.  He reached over and gently tapped her hand and she put it down face up on the table, and in about 2 minutes picked it up again, all while chatting with him and occasionally showing him something she thought was funny. She could have stayed home in t-shirt and shorts and read her phone messages. It would have been a lot cheaper--and less rude.

And then the big shocker.  She apparently had a shoe problem or maybe a toenail was irritating her, so she brought her knee up above table height and was fixing whatever was wrong. I hope this was Dutch treat, because the young man deserved better.