For photos, you need a story for how to do something that's equivalent to "share publicly" without the implications that that usually comes with on a social network.

There are photos on G+ that I'd like to show my family. This is "public" from G+'s point of view, because I'm not going to make them log into G+.

Nothing goes wrong if other people see these photos too; however, I don't want people who have me in their G+ circles to get notified that I'm now "sharing" these photos that they have no interest in, and I don't want some boring photos to represent me on my "feed".

This use case worked on Picasa, but G+ broke it.

Right now I find the extremely concealed download link and e-mail them. This is not how a photo product should work.

Totally agree with you.

What I meant isn't that any product gets it right ATM but rather that there isn't a good technical or, I guess, social reason for why galleries couldn't be a killer social feature. It seem there are a few economic/marketshare etc reasons though.