Why are engineers spending their week-end on saving their company money especially if the company clearly doesn't care to allocate resources to the problem?

I get that it's fun and there's personal satisfaction in it, but it just reinforces to management that they don't need to care about allocating resources to optimisation, the problem will just take care of itself for free.

At some point it's hard not to care about the work you do everyday. And if you care, then you are going to find yourself donating a Saturday here or there to solving big DevEx papercuts that you can't convince management to care about.

Should it be this way? No. Is it this way in practice? Unfortunately often.

A cynical take is that this makes them more hireable, so they can more easily get to a better company with not-so-brain-dead management

This also explains this blog post