Maybe there’s an also genuine - and justified - change in people’s concerns about how their photo will be used. Probably 99% of these photos are now taken with the intention of sharing them online in some form, so the potential for your image being used or exploited in a way you don’t like or approve of, and seen by many thousands of people, is hugely increased. That risk was just not the same in the 1960s and 70s.
Also there’s always been a surreptitious aspect to it and some photographers are just more comfortable with that than others - people were using concealed cameras to do candid photography in the 1930s.
Maybe there’s an also genuine - and justified - change in people’s concerns about how their photo will be used. Probably 99% of these photos are now taken with the intention of sharing them online in some form, so the potential for your image being used or exploited in a way you don’t like or approve of, and seen by many thousands of people, is hugely increased. That risk was just not the same in the 1960s and 70s.
Also there’s always been a surreptitious aspect to it and some photographers are just more comfortable with that than others - people were using concealed cameras to do candid photography in the 1930s.