They definitely have other intentions, but it's often the same as people contributing in their free time: they use the software, want to make it better for their purposes, but don't want to be the ones to maintain it.

Don't we all have "second intentions"?

Altruism happens usually among members of a tightly knit group, like family members or soldiers of a given unit. Teachers sacrificinng their life to save children. FOSS-developers, are they really producing software out of altruism? Maybe some of them are but it is hard for us to know whether that is so or not.

If a FAANG releases Kafka, REACT, Kubernetes, or any number of projects that they found helpful, and released into open source - there will always be a claim that they do it with some second intention, such as "be seen to be a positive contributor to the community"

But the truth is - so do I - as a humble contributor to a document, test, bug fix, or feature add to a FOSS project - where's the beef?