This is my primary explanation when I lived in the city. I would walk my dog to the top of Buena Vista park nearly every morning at sunrise and marvel at the city in awe.

Just to clarify for those who won't fully understand this.

The temperature range is very tight and mild so you don't need to think very hard about how to dress for the elements. For me jeans and a tshirt was basically year round attire. When it rained the extra warmth of a rain jacket was enough to offset the slightly cooler weather. You can run outdoors year round, save for a couple weeks of heat wave, or a bit in the "winter" if you refuse to run in the rain.

However, it's not the sunny beach, wear a bikini / no shirt weather that many have come to understand of California from hollywood movies.

Schwalbe make some great commuting tires but I doubt they can withstand discarded needles.