Making notes of information incidental to the case enhances interactions. The more personal details you retain, the more intimate the interaction and the greater the sense of personal attention.
Compare & contrast the following:
Last time you said you were going on holiday with your husband and daughter but you were worried about the journey: how well did it go?
Two weeks ago you said you were going to Greece with David & Sally but you were worried about the flight: how well did it go?
Item one says: I was listening. Item two says: I was really paying attention.
If you forget the name of the client's dog or make disparaging remarks about a TV programme the client once said they liked, you will probably be forgiven. Clients are (usually) well aware that you have more than one client and cannot be expected to remember every last detail of their lives...but, in an ideal world, it would be nice to do so.
J. A. Foley (campaign manager of the US President F.D. Roosevelt) kept notes of the incidental information (children's names, hobbies, pets) divulged by anyone met by the President. Days, weeks or years later, Roosevelt could be reminded of this information for his next meeting with them. This may seem insincere, but it was the information he would have carried in his head if it were possible to keep track of so many people.
Professional case notes should contain the information pertinent to the case: symptoms, time course, beliefs, treatment plans, etc. It is these issues for which the client is consulting you and on which your attention should be focussed. Get these wrong and the client's faith in you will be diminished.
Keeping a "Foley file" of incidental data frees you to concentrate on the data pertinent to your intervention. Process notes are the place for impressions and half-thoughts, but can also be used as a Foley file for the trivia which, given a perfect memory, you would wish to retain.
In your casenotes you will record the data which is meaningful to your professional role, but in your Foley file you can record the data which is meaningful to your client. Get these right and the client's faith in you could be enhanced.