[Johnny555]

Again, who said anyone is getting anything for free?

My company has 100+ engineers, all of whom do a on-call rotation, they are all aware of it when the sign up, so that on-call duty is included in their salary. The employee can evaluate for themselves whether or not they think the salary is sufficient to cover that, but as far as I know, we've never had a candidate turn down an offer due to the on-call requirement (though I don't know that they'd always tell us that's why)

But really, does any engineer join a small company (in the USA) without assuming that they'll be on-call after hours? Even in early stage companies that haven't launched a product yet, there's still after-hours support to be done to keep dev systems running, fixing broken builds, etc.