It's more meaningful than using the honor system.
And it's not your "medical file" a lot more than your driver's license is. It tells one significant detail about your medical history, and that is it.
I prefer bars where I know I am safe, and one where there are people like yourself who claim to be vaccinated but resist showing proof, don't make me feel safe.
If you have hemorrhoids that's no ones business. If you're going around spreading covid that is other peoples business. And they have a total right to protect themselves from you.
It is the honor system. Anyone who wants a blank CDC vaccination card doesn't have to look far to find one. Requiring them as proof for anything is just a bureaucratic checkbox.
That doesn't make it the honor system, except to people who are unable to see shades of gray.
In my country, by law, you need to show a certificate to sit inside restaurants and bars. The government built a system that generates a QR code for patrons which can be scanned by merchants - with a government app - to verify it. The QR code has the data encrypted so no personal data is shared with the restaurant. I'm not sure if it sends anything back to the government (I guess not because of GDPR).
It's worth mentioning the certificate isn't just for vaccination. You can also get it after recovering from Covid (valid for 6 months after positive test) or had a recent negative test (valid for 3 days). Going the vaccination route is the simplest option though, so in a way it is forcing people to get vaccinated if they want to resume normal life.
There’s no public Heath guidance to check for vaccination, so this is just bars trying to be overzealous.