A lot of that has to do with the originating country.
You may have to have vaccination proof before you can board.
I don't live in the US. Where I am you have to show proof of vaccination once you're back home.
Here, they track passport scans (biometric) from the airport and you'll get a notification from the local health authorities to provide vax status a day or so later.
Not in Germany it won't.
Depends on the state, but in some students are tested every day. if they're not vaxxed.
This may be someone's "take" on the the process of teachers asking who still isn't vaxxed so they can be sent out to testing.
Big fake vax records scam going on, too. That shit pisses people off. Positives don't quarantine, either.
If anti-vaxxers just used the alternatives they'd get more sympathy. Like anything else, too many assholes trying to be sneaky.
Huge anti-vax hate in Germany. That why the demonstrations are going nowhere.