Not saying that is necessarily the case, but situations like this can also develop if you have a lot of basic knowlege (especially regarding tooling) that is neither documented properly nor spread amongst most of the team.

I've had scenarios where I spent an afternoon building a little one-off application I needed for some specific debugging task only to be told a month or so later that someone already built a proper tool for that - but only one developer knew about it, and it was stored in a different repository I had no access to.