"Why are speaker companies still tweaking designs of speakers?" New models = new reviews = new press coverage. New factories open and old factories close. Different and/or cheaper engineering solutions are developed to work with the firmly established, stable, highly confirmed, well understood science of acoustics. Different subjective preferences are catered to. Lots of reasons.
Of course there are things science doesn't understand. That doesn't mean you get to imagine whatever you want, or to ignore what science DOES already know with a high degree of certainty.