This is pre-Covid:
> easily accessible nature
From my office in Palo Alto, I can ride my bicycle up Sand Hill Road, past horse farms, and then up a secluded 2000 ft (~600 meters) mountain with virtually no traffic and return during my lunch break. Or I can take a long lunch and ride out to the coast, through rolling farmlands. And I can do that virtually any day of the year, thanks to the local climate.
Most of the peninsula (which is, arguably, not SV proper) is like this, with tons of hiking within walking distance of where you live or work. The reason is that almost everything west of I-280 is undeveloped. As you ride or drive around that area, it's very easy to find a view where the only sign of humans is the road you're traveling on.
If I want to go skiing, I can leave work an hour early and drive up to Tahoe for the weekend. Or I could drive down to Santa Cruz for the day and go surfing.
Not quite "nature", but many people like to drive up to Napa for a day-trip to visit world-class wineries.
> luxury retail
Then, after work, I can walk over to my choice of Michelin starred restaurants (and I will pass multiple art galleries and branches of private banks). Granted, none of the restaurants in Palo Alto have more than one Michelin star (how gauche!).
If conspicuous consumption is your thing, San Mateo, Palo Alto, and Santa Clara each have high-end malls with practically every luxury brand you can imagine. Want to buy Ferrari or a McLaren? There's a dealer for each one within 10 miles of Mountain View.
> plenty of places all over the country that fit this bill
Many places have some of what SV offers. Very very few have everything, and I would argue that none of the cities you listed fit the bill.