There's a secondary common-knowledge/coordination effect here, though, it's not just “individuals being lazy”: if someone gets antsy about whether ey will look awkward in front of eir friends for making the assumption that they will be willing to spend on something, then that feeds into the feedback spiral of “I don't really believe it'll work and I feel reluctant and don't want to tell people about this in case it's uncool”.

A colleague of mine said that this suggested what was really necessary was to allow simple prosocial spending that wasn't too in-your-face, along the lines of how it's possible for one person to rent a game server for several people. Less individual anxiety over spending, since among other things there's enough of a social script for that.