OP here. I can do all of that on my MacBook/Ipad. Heck, I can even call people on my flip phone. Sometimes I even visit my family in person!
One way to look at smart phones is as extensions of your computers or in the case of the iPad, a miniaturized iPad, but one that will always have connectivity so that you don't need wifi.
A lot of people who use smart phones use them for functions other than voice or texts, though iMessage in iPhones is more than texting as you can use it to communicate with people around the world without paying international texting charges as long as they have an Apple product as well.
You can also use the hotspot or tethering functionality on a smart phone to serve as a Wifi connection for your MacBook or iPad if you happen to be away from home and you don't have access to wifi.
Even if you have public wifi like at a Starbucks, you'd have a more secure connection using your smart phone as a hotspot.
My mother uses an iPhone and she doesn't use any of the smart phone features, other than using the Phone app. to delete voice mails or remove old calls in the call log.
But she didn't like carrying a simple phone because they were cheap and her friends had iPhones. She always uses the speakerphone and she hears better this way than using her landline phone.
One thing about sound quality, many smart phones will support wifi calling, where you can boost the sound quality of the voice calls when your smart phone is connected to the Wifi network. But not all smart phones have wifi calling so that's something to look for.
As for people constantly staring at phones at restaurants, a lot of that is from social media so if you install and log into Facebook or Twitter and turn on notifications, the phone will constantly pop up updates and people have said that that may not be a good thing for brains, to be kind of Pavolovian about needing to always look at updates as soon as they appear.
