As someone who lives in the Hamptons year-round, I've driven into NYC and back on a single charge many times, and usually end up with about 20-30 miles of range left. But unlike summer weekend visitors, I don't have to sit in traffic both ways, which can cut down on range significantly, especially if you're blasting the AC while sitting in that summer traffic. And Montauk is a good 25+ miles east of me, so add 50 miles to anyone heading out there.
There are some destination HPWCs already in the Hamptons, but it's not like they're at the beach! We've had our HPWC listed on PlugShare for almost three years, and while I'm sure the many people that have stopped to charge there appreciate it, I'm also pretty sure that they would rather be doing any number of things rather than sitting in our driveway for a couple of hours
And, as HollywoodNY mentioned, the Hamptons summer visitors are definitely part of Tesla's target audience, which is why they host/sponsor many events in the Hamptons...So, while a Supercharger out here will certainly be useful, I think it's just as much of a marketing/promotional opportunity from them as well (and, I've had the Tesla guys charge at my HPWC more than a couple if times) Is it essential? Is it a top priority? Probably not. Which is probably why they waited almost four years to install one out here.