Square watches do exist e.g. Cartier Santos and they do have ergonomic advantages. Smartwatches are not alone in the trend of watches being huge. Most watch brands have started making more 43mm+ size watches which I find far too large. Smartwatches also have it a little harder as well since it is going to be really hard to get much info on a screen at 40mm or smaller, especially when you cut off the corners. Most smartwatches are around 45mm, Apple making the smallest at 40mm, but I prefer watches that are in the 36mm - 39mm range.