A side-project isn't by definition irrelevant, and of course by sheer probability the engineers at those companies are, on average, going to create things that are within their area of expertise which is usually related to what the company they work at does :).

The motivations for making software OSS are varied and often strategic. For example software is often open sourced to:

* deliberately commoditize it - to eliminate competition and differentiation in that area / stack layer * leverage additional (free) testing and development. * Drive ecosystem / platform adoption * Literally free up customer budgets to be spent with them, rather than on licensing 3rd party software * Intangible benefits like community image, employee satisfaction, etc. * Some combination of above when the software is useful internally, but simply not in a market that the company wants to compete in, or a market worth their time

In any case, the point was that they are "side-projects" from a business perspective in that they cost money but don't generate revenue - the benefits are hard to quantify. Successful, stable companies have much more breathing room for strategic and the "hard to quantify" ROIs than does a company on a trajectory towards bankruptcy. It is kind of like an individual out-of-work engineer with a month's expenses left in the bank choosing to contribute to OSS instead of seeking out paid work. It is not that contributing to OSS is wrong, it is that the priorities in that situation are backwards.

RE: "Nobody is forcing Uber to employ people in California." That is entirely true, but I'm not sure what your point is. My comment is a post-mortem on what led to the layoffs. It is a priori that nobody has forced Uber to do anything that it did...