why is castrum and praetorium not an instance

[Nezerius]

It's come up that often because it really is an important problem. The fact that it's been a major problem for a lot of people doesn't make it less important, it makes it more important.

The fact that it's come up that often, and has yet to be fixed, clearly means that it's not as important to SE to fix it. I imagine it's way down their to-do list on QoL fixes.