I am surprised at the number of people who don't already have records of where they've been. For social occasions - e.g. going out for dinner or having visitors at home - I would always have that in my diary anyway. For more casual things like buying lunch during the week I would have my bank records to refer to.
Yes, I understand that there is an advantage to the tracing app in that it can provide notifications but I can't see any benefits beyond that.