Another possible explanation is that Tracker is so old that BTabView didn’t even exist when this window was created.
The UX design is not great, the almost empty list view doesn’t look so nice and wastes space. The tabs are obviously a better choice here with just 4 options. We can change back if someday we want to add a lot more options.
There is the Auckland Layout Editor, and no one uses it. There are also many older tools from BeOS days (not using Haiku Layout APIs), and no one uses them.
Can you elaborate? It looks like the opposite to me. Tab View causes the mouse travel to at least quadruple to switch to the next item, forces a horizontal mouse movement (which is a more muscle-taxing movement), and it causes to lose easier keyboard navigation.
It is possible to fix this issue via auto-resizing the window vertically as well. It only auto-resizes horizontally at the moment. It will benefit other system components too!
I’d say that this crosses into form-over-function territory.