10+ years ago, I forgot to take my phone out with me for a post-natal medical appointment. I'd had a rough pregnancy, and a rough birth. DH was giving me a lift home... when I called him. The appointment was dealt with quite quickly and I staggered slowly to the only payphone in the neighbourhood to find it broken. (It now no longer exists as of some years). The pub next to it wasn't open yet. Faced with a choice of staggering slowly back to the GP to try my chances at pursuading them to phone DH (I knew the phone number) or staggering on, I thought I may as well plough on compared to the effort of doubling back. It took 20 minutes to do what would be a 5 minute walk to a healthy person.
Society revolves around the assumption that you have a mobile phone. You can't just leave it at home and pretend it's still 1995 and that those adverts declaring "the future's bright, the future's orange" is an enigmatic mystery. Well you can leave it at home, but you then risk relying on other people because there aren't the payphones any more and society has moved on.
DM never got into the mobile phone thing, and certainly never sullied herself with things like computers and the internet. The reality is that all she's done is make herself very hard to communicate with especially now her ears and legs don't work well enough to pick up the landline in time, and she delegates all the essential computer stuff onto DB or her friends. She is not genuinely living independently of it.
I keep my cards with my phone for space reasons and have since cash was treated akin to toxic waste in 2020, so that means both go together. The advantage of that is that I no longer need to go running with jingling emergency small change for snacks or bus fare. The only regular thing I do without them is the short school run as it is such a minimal distance and chances of emergency child issues is minimal. Social arrangements like the pub or going somewhere secluded like a cemetary, I would take them in case of change of arrangements or personal emergency.
I haven't forgotten how to live without a phone handy at all times, but gone are the days when you needed 10p for the nearby payphone to resolve any issues.