Gertrude, what you say makes perfect sense, it's logical, and many people would say much the same. But accident history is littered with examples where pilots have done things (and often we'll never know why) that appear to defy the logic you set out.
Given that we often cannot ask why the pilots did what they did, we must try and second guess why the various decisions that led to the accident were taken. So when a group of peers, while sitting around a table with lots of time to cogitate, have to try to put themselves in the pilot's position sometimes the only explanation for some of the decisions that were taken is to avoid a landing fee or something equally minor.
If we are to make/keep aviation as safe as it can be we have to learn why accidents and incidents happen. Trying to understand why an accident has happened without the benefit of input from the pilot is not a perfect science but there is no alternative.
I'm fortunately not often involved in post-accident investigations but I believe that when the pilot is able to participate it is surprising to find that the logical decisions that are easy to make on the ground are not necessarily those that are made in the air.
I imagine it is this background that led the CAA to encourage airfields to waive landing fees for wx diversions.