Cabasse also makes square/rectangular speakers. They may also have some patents on them so other companies cannot make similar ones. And of course the way they sound might not be to every one's liking, regardless of research, science or technology. I may be wrong, but I don't think anyone makes a round Sub Woofer (KEF did made one that looked like a car tire).
Wilson has sent tens of millions designing their speakers and they are not at all rounded. PS Audio just spent millions designing a slightly round box speaker. If round was the perfect solution, both those companies would have not used boxes of any kind. Besides, the 1970's were a loooong time ago. I am sure the research has advanced since then.
I myself own Harbeth 30.2's which get trashed all the time for being thin-walled and using basically paper cone speakers in them (talk about old technology!), but I've compared them with speakers up to $12,000 (bookshelf size only, not floor standing) and found none as 'natural' sounding to my ears. It's not just the materials and design, it's the ear of the designer.