Even if you don't enough people do. My wife still uses FB. Amazon just came up with echo in frames. The privacy quickly becomes a luxury available only to select few.
Not only that, but some years back there was an expose about some government profiling software marking people as more likely to be terrorists if they didn't have a social media profile.
Were you paying with a credit card? In Argentina the norm is to ask for id when paying with credit card, and if you're a foreigner the default would be to ask for your passport.