The problem isn't the advancement in phone technology. It's that it affects things that have nothing to do with cell phones. In other words, I shouldn't need a phone just to adjust the heat in my home, or to use a camera. Using your analogy, it would be like not being able to watch TV or use your refrigerator unless your car was nearby.
The point is don't put all your eggs in one basket.... The car is a car, the phone is a phone. Think of all the stuff you can't use if your phone breaks.
Of course, this doesn't even consider the phone zombies. Any time we go to the mall or a restaurant, every single patron is walking around with their noses in their phones. People aren't interacting, they're not watching where they're going, etc. Heck, I often see people using their phones while they're driving (yes, it's illegal, but people are addicted).
As others have noted, smart phone is a computer with communication capabilities which always let you be online.
Yes phones store financial, health and other personal data in one device.
That can be bad if lost or stolen or you're locked out somehow and unable to access all the data you've put into the device.
OTOH, you have everything in one place. It sure beats separate pieces of paper or notebooks.
Or remember back in the day you had savings account books or check books to track your finances on top of tons of paper statements?
I still have a lot of paper statements from my brokerages going back 20 years. Got to get to shredding them.
When my father passed away, I had to find all the bank accounts from all the statements he had all over the house. He used computers and smart phones but had never organized all that data. He didn't use a password manager for instance.
I had to get account access by showing his death certificates. In the course of this process, I found accounts worth hundreds of thousands.
You don't have to access your financial accounts from a phone. You can use a browser to log in.
I use both, including times when I'm away from my computer.
Phone is a digital Swiss Army knife. Again you don't have to use it that way to store or access all your personal data.
But you don't have to use a computer either. Banks and medical practices will mail you paper statements still. You can manually balance your checking account too.
Computers and phones make it a lot easier.
As for as risk of data being stolen or lost, modern phones have remote tracking capabilities and you can even wipe data off them remotely if it's online (has a cell or wifi signal).
If not, there pretty hard to break into. I once lost an iPhone in Amsterdam and it never went back online. However, I sent a message to it with my contact info. and after I returned from that trip, I got a couple of phishing email attempts, trying to get me to log into iCloud.
But it was a fake iCloud site, the URL was nothing like iCloud, so if I entered my iCloud password, they'd be able to unlock my lost iPhone.
This was an iPhone 4S or 5S, almost 10 years ago.
iCloud activation lock has been pretty much solid, even led to fewer thefts of iPhones because they can't be broken into without your iCloud account password.