Responding with a general 'why not' is not an answer.
If it's no use, then why clutter the UI ?
When you're a big realm, it's annoying looking for other people when you're looking at your same folks already that are available in the other tabs
If you look for someone general, why not use "Search all" immediately ?
How often does it happen that you use the "Search realm" (let's say with same culture and religion) first and only then look at the "Search all" tab ?
I see that that can be al little bit of a hassle, but how often does this happen ?
Even if, there are filters still.
If you're looking for a specific person that's no longer in your realm / a specific culture etc. Is it practical for most? Probably not.
Specific character search is even easier.
You know you can reduce the search results with
filters as culture (group) or not culture, the same with religion and others, you can
use the
search box to type in some keywords, as parts or whole words of names or traits or dynasties if you search for someone special ?
..and even sort the results again by clicking on the
tabs of Name, Dynasty, Culture, Realm, Age.
Just use the "Search all" tab right away...and aforementioned.
...Of course nothing holds Paradox back cluttering the UI further, similar as the character screen,
so who knows..maybe you get your wish. Me rambling more or less against something in such detailed manner as i just did,
increases the chance of it by my experience.
Don't get me wrong, i'm not against it per se, but not for it by simply adding it.
Maybe a seperate 'more options' button opening an additional window with more filters....hmm no,
that reduces accessibility...hmm...
There is a Suggestions subforum.
edit: heavily edited..