This is a totally valid point, but it does make me wonder: why don’t psychotherapists behave in a similar manner to lawyers with this type of disclaimer? Maybe because it’s not a therapy session unless you sit down for an hour in a private office?

People get self-aware of the dangers related to their profession. We get pretty crazy about data leak, when nobody else really cares. I'm pretty sure the psychotherapist you just talked to at a dinner party has one or two diagnostics on your mental health and has an opinion on your relation with your parents, and lawyers always think about what can get you sued. So they get really careful when there's a legal risk for them.