Everything is safe if no one else is doing it, I imagine the concern is that even hiking trails can get crowded. Not if you’re off in a super remote place, but if you’re near a big city and a large percentage of residents all want to go for a hike within 30 minutes of where they live on a Saturday morning, the trails will get crowded. There are bottlenecks like a narrow part of a trail or the public bathrooms where people will have to come into close proximity. And of course you will have people that will inevitably meet up with groups of friends they don’t live with on the hike and spread it that way.
If everyone were to hike as responsibly as possible it would be fine, but in terms of broad stroke rules for public health, it seems you have to err on the side of being more strict than you would be just for yourself because people are always bending the rules and acting unpredictably (whether intentionally or not).
If everyone were to hike as responsibly as possible it would be fine, but in terms of broad stroke rules for public health, it seems you have to err on the side of being more strict than you would be just for yourself because people are always bending the rules and acting unpredictably (whether intentionally or not).