That's an interesting observation, though I think you've missed the effect of scale. Keep in mind, a one block town would be 100% accessible by a public transportation system consisting of a horse drawn carriage on permanent loop.

More of Portland is accessible by public transportation than the SF Bay Area, but then again, in absolute terms, there's notably less Portland to be accessed. I'd say that what you can access on public transportation in the SF Bay Area vastly exceeds what you can access in Portland, mainly because the SF Bay Area is far, far, bigger. There's also a lot more that you can't access in the SF Bay Area (and if you work in tech, you may be forced to access it).

One way to illustrate this would be to overlay a public transportation map on top of population density map based on census tracks. You'll see that there are far more high density census areas in SF/Oakland serviced by light rail, subway, bus systems, and so forth than in Portland, and that the areas connected offer vastly more in the realm of commerce, entertainment, arts, sports. The same will be true of Seattle was well.