9/10 times they haven't set the permissions to receive files through airdrop. It used to be open, but that was a huge security vuln. People could just airdrop whatever picture they wanted to all the iPhones on an airplane for example
There was also a certain amount of regulatory pressure brought to bear; Hong Kongers were using AirDrop to great effect in outwitting the authorities during the 2019-2020 protests
That's 0/10 for me: I know I have the correct permissions set up with my friends (because we can usually Airdrop each other), but sometimes it just spuriously does not work.
One thing I've noticed when AirDropping pictures to my wife is that the recipient needs to have their phone _unlocked_. That was definitely somewhat confusing when I first started using the feature.
