I can go see thousands of migratory birds a few miles from my apartment. Half Moon Bay is 30-45 minutes away, depending on road conditions. Fairly strenuous hiking and rock-climbing in the Santa Cruz Mountains is also 30-60 minutes away. Santa Cruz itself is not much farther.
I have lived all over the east coast for most of my life, and this degree of access has made an outdoors person of my notoriously sedentary self.
So can I, as I mentioned there's a major state park within the city limits where I live...
> It means I can see a beautiful view without planning a day trip.
Incredibly vague and subjective. What constitutes a "beautiful view"?
> I can meet with groups of friends of all fitness levels and enjoy a pleasant afternoon outdoors where we all have fun.
Not unique to the SF Bay Area at all.
Again I think this is very much a cherry-picked definition of "easy access to nature" that is designed to preclude any place not named "SF Bay Area." Still, the kinds of things you were describing can be found in metro areas all over the country.
Define "easy access to nature." Where I live, there's a major state park within the city limits and a very large lake within ~20 minutes drive. In ~2 hours I can be at the beach. In ~3-4 hours I can be in the mountains. And untold amounts of basically empty land just outside the city. If you're going to arbitrarily define "easy access to nature" as "mountains next to ocean right next to me", well OK, not a lot of places fit that bill. But that's a very narrow definition designed to fit basically SV.