[dragonwriter]

> AWS does tons of stuff around VPCs....I feel like they really want me to use them (or their customers really want to use them)

VPC is a very convenient fit for enterprise customers extending on-premises networks into the cloud, I think that's the market it's mainly focussed on.

> I know it's "public", but that seems irrelevant in the era of cloud services.

It's not irrelevant, but neither is it necessary critical all the time; there doesn't need to be a one-size- (or even one-shape-)fits-all universal approach to network security, and AWS encompasses a lot of different customer setups, including enterprises for which it is a virtual extensions of the on-premises internal network.