I wouldn't chat with strangers sitting on a bench with or without a phone. I say this as someone who often walks in parks without taking out my phones. If there's a claim that my not talking is affecting other people's health, I'll counter claim that such a burden of socializing is a kind of peer pressure, and it is negatively affecting my mental health.

> We are simply wired to function in social groups.

A stranger on the bench is not my social groups. I have my friends and circles to whom I talk, and that's good enough for me. Talking with utter strangers on random occasion is stressful to me; I'm quite certain that I'm not wired to do it.