I've had my P85 for 3 years. For most of that time, I had an HPWC at home at 80A using both chargers, with several extended periods when I only had access to 40A using one charger.
For home use 40A and a single charger is probably all that most people need. The only time I've really needed to use the dual chargers at home was when I did a lot of driving during the day and needed to recharge to do more driving in the evening - which hasn't happened very often.
For trip use, we have found a destination charger at a nearby hotel when visiting family - and that charger runs at 64A with the dual chargers - and it has been useful to charge faster after we first arrive - and put on enough charge to drive around town in the evening.
For most people, purchasing the 2nd charger is probably more of a "range anxiety" solution - knowing that you have the ability to charge at up to 60 miles of range per hour, if and when you ever need that - but probably something that may never really be needed.
I also invested in a bag full of adapters - so I'd be ready to charge using dryer plugs - if I couldn't find a nearby charger. This was a much larger concern 3 years ago - but today with more superchargers and destination chargers, plus the commercial EV charging networks, I haven't had to use any of the adapters for a long time.
As for the HPWC, without the dual charger, the HPWC doesn't provide much benefit. It is a little more convenient to use than the standard charging cable - and looks nicer on the wall than having the heavy charging cable plugged into an outlet. But, without a dual charger, the HPWC won't provide any benefits for charging over the standard cable.
That said, if/when we purchase our next Tesla - we'll likely still purchase the dual charger option, though we'll probably plan to only have one HPWC - and use a 40A circuit to charge the 2nd vehicle.