One of the problems with their "better / worse" statistics: Bad interactions tend to outweigh good interactions. I think the rule of thumb is that 4:1 good/bad ratio in a relationship is "breakeven" where the relationship will stay neutral; higher than that and things get better, lower than that and things go south.
So if you could talk to a stranger, and there's only a 20% chance you'll feel worse, a lot of people would still not consider it worth the risk.
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