I live in Seattle (south end of Ballard). I can jog to Discovery Park and be in forest surrounded by beach, or up to Carkeek and see tide pools and wetlands. I can be on a real hiking trailhead in less than an hour.

Camelback Mountain is half an hour from the center of Phoenix. Virginia Key Beach Park's walking trails are 20 minutes from downtown Miami. Lionel Hampton-Beecher Hills Park is about the same distance from Atlanta. You get the idea.

SF certainly has really nice nature close by, but it's not like other US cities are industrial wastelands.