Enforcement. You need to be able to set rules, you can enforce easily. If you allow single person walking, what will you do if you see 2 people close to each ot

Enforcement. You need to be able to set rules, you can enforce easily. If you allow single person walking, what will you do if you see 2 people close to each other. People will always try to avoid the rules, so in this kind of stuff enforcement is really hard. Better to have hard but short lived restrictions.