Agreed; and there's also a selection bias: The most visible, active, HackerNews population is likely to be (for whatever reason) more involved in opensource and side projects.

Whereas, in the overall population of IT workers, that percentage will be far far smaller.

For what little it's worth - I'm now a middle-manager (ick) in a traditional large IT company (ick ick), and neither myself nor the recruiting / HR teams I work with have ever once looked for, demanded, or even seen side projects. The UNIX SYSADMINs, Oracle & DB2 DBAs, VMWare specialists, application developers, testers, etc... they're all dedicated professionals but not necessarily zealots. Some of them will tinker and do certs and play with stuff off hours, most of them don't, but all I strictly care about is can you do your actual job professionally when and where I'm paying you. We do encourage learning, and have incentives for taking courses, reading books, etc. But we don't expect you to do unpaid work. As a sibling comment indicated, on operations side we work hard enough that I encourage team members to unwind and take care of their family, needs, hobbies, mental health, life goals etc when they're offline.

(My personal 100 Croatian Lipa, all opinions are my own, etc :-)