I have however started to realise that perhaps something I thought would be very useful may be of little interest to anyone else. Furthermore the effort I have put into testing and documentation may not have been the best use of my time if no one but I will use it. As my time as a post doc is limited, the extra time effort spent on improving these tools could have instead have been spent elsewhere."

From a purely selfish perspective, I've found that documenting and cleaning up my own code benefits me in the future. Even if it's a one-off, single-purpose utility that I'll never use again in the future, I often find myself needing to borrow bits of code from my old projects. ("Oh, I solved this problem before. How did I do it? Let's dig up that old, old project...") At which point, present-day me benefits if my past self bothered to actually document things and make sure they're reasonably robust.

There are countless other reasons (moral and pragmatic) to document, test, and open-source one's code, of course! Many of them more important than the ability to crib one's old code, I'd argue.

But the author seems to have considered (and discarded) them...