I grew up in the Wmt. Valley, worked for a couple years in the NY Metro area, and have been living in the Seattle area for 10+ years.
Just guessing, perhaps 50% of the population has immigrated from other areas of the US in the last 15 years for professional level jobs and are working long hours. Add to that the fact that culturally earlier settlers were English, Scandinavian, New England-er, Japanese and Chinese (typically Cantonese). The first four groups tend to formal until they know you well. Cantonese Chinese are gregarious within their own ethnic group and with others they know well, otherwise they are also formal socially.
Most social interaction is affinity group based, whether it be cycling or genealogy.
In Portland Thirst Thursday is the evening to get out and mix. There is a very active singles group that sponsors lots of activities. There are a bunch of us 'old farts' who didn't appreciate the newly arrived fuddy-duddes quashing a favorite fund raiser: the annual pub crawl for the symphony. Honest, we do party.
We have our full quota of odd-balls, but generally folks don't intrude in the private business of others.