I do have limits on what I will do with my phone. Anything to do with the transfer of MY money, I will not do. Tik Tok, or Twitter, no way. There is a bit of Facebook, but that's just uploading a photo or answering an IM from a friend or two. I see those maybe once a week.
I do book flights and use my phone to check in if I'm only flying with carry-on. I book my hotels and rental cars with the phone, too. I can do all three in about 10 minutes. I can also do my expense reports on my phone. That there is a great time saver. Most of the QR codes I run across are for restaurant menus. I don't like it, but whatchagonnado.
As far as youngsters, we had a new hire that I took out in the field with me who insisted that I text him. If I leave him a voicemail, he will not return my call. My reply was I'm not going to text you. If I leave a voicemail and you do not return my call, I will fire you. End of conversation.
My boss, on the other hand, should have his phone surgically implanted. I don't mind answering a question or two via text, but he likes to do twenty question text fests. When he gets like that, I tend to ignore him until he calls bitching at me. Then I answer his questions.
As far as costs go on this side of the pond, the price of the phone is built into the contract, usually two years. After the two years, the phone is yours. The problem is that many of the most popular phones out there barely have a lifespan of two years. I never got more than 18 months from a Samsung before they'd start to go nuts and die. Earlier LG phones were better than the newer ones. My current phone, a Kyocera DuraPro 2, is a mil-spec unit, tough as nails, three years old, still going strong, and was hundreds of dollars cheaper than what AT&T tried to sell me. Sadly, discontinued.
My siblings all use Trac-Fone, which is pay as you go. As none of them have traveled as much as I have or needed their phone for their jobs, it works great for them.