Why do we still need apps like AppCleaner to remove apps properly?

I am wondering about this for some time now... Why is it that macOS does not remove all the hidden data that apps like AppCleaner will remove when deleting an application? Why do we need a third party app for this? Would it not be much better if macOS would do this for you as well? I know you can find all that metadata yourself if you look for it, but most people just drag the app to the bin and think it's all gone and good. It should be so easy for Apple to implement a feature to find all that metadata as well when an app is dragged into the bin. Right? Or what am I missing here?