There’s no copyright involved in taking a picture of someone, or having a picture of someone… Your tourist pictures are fine. If you publicize then or try selling them, that might be an issue, but making it inconvenient for people to make money off of non-permission photos isn’t really concerning to most people.
Basically ‘duty cycle’…same reason electric heaters all put out 1500W but ones for larger rooms are ‘larger’. Big or small, they both put out 1500W, but the small ones can only do it for a few minutes at a time before having to cool off, while the larger ones can run for longer and heat up a big room more quickly.