having looked at close to 500 speakers,
https://speakerchoices.com/ rectangular speakers are generally cheaper to make/ and are priced lower. Small boutique shops in the lower price range won’t make curvy speakers.
You won’t find a significant SQ difference attributed to shape is my guess. Most "fancy speakers" tend to have a teardrop top profile - narrower at the back, which is embracing the shape of the driver. It’s more pleasant to look at, exudes higher quality, therefore can be sold at higher prices.
Contradicting that is the vintage look (boxy with wooden surfaces) that also sells to a certain clientele. The loser of this race is the boxy modern look.