Is it purely design preference or were you conditioned to like round watchfaces because you were surrounded by them all your life? If you mostly saw rectangular watchfaces all your life, do you still think you'd prefer a round watchface? Also, if it was purely a design preference wouldn't that same preference also apply to computer monitors and smartphones? Because that's what a smartwatch is... Just shrunken down to fit your wrist.
I ask those questions because having worn the Apple Watch for over a year now, I actually find round watchfaces a bit odd now, even though I've worn them most of my life. Also, every time I see a round smartwatch display data, whether it be text or image, it reminds me of just how impractical it is... It's literally like looking at a round smartphone, just smaller.
People don't wear computer monitors and smartphones, or TVs, or laptops, or movie theater screens, or any other ridiculous comparison you can come up with. That said, it's the darnedest thing -- people do like to put rectangular photos into round picture frames! Go figure.
Now, people do wear eyeglasses. And using your logic, it doesn't really make sense to offer any other shape of eye glasses, since the rectangle offers the best field of view for the way people see. Do round frames work better? No, different shaped frames just makes it harder to come up with lenses that provide effective vision when they have to account for so many different shapes.
So why not have all eye glasses be the same shape. Just offer two sizes of the same frames, rounded rectangles to accommodate all face shapes and genders, and then standardize the lenses for every pair of glasses in existence.
Customers still have lots of style choices, they can chose different frame colors, they can even choose removable temples to allow them to dress up their frames, or tone them down to be more sporty.
And mostly because fashion doesn't matter for a product a customer wears ... right? /s
