Culture is shaped by biology. East Asians have a relative strength in spatial ability, which may explain their use of pictographic writing.
(Chinese and Japanese writing systems are actually properly called logographic.)
Korean isn't logographic. Nor are Thai, Burmese, or Cambodian. Alternatively, Egyptian hieroglyphics were logographic. Though a variety of new world languages used pictographs for writing, as do a few languages in and around Nigeria and old Chinese writing systems. Etc. So logographic and pictographic systems show up all over the world.
Burmese letters are rounded: people originally wrote on palm leaves and straight lines would have torn the leaves. So in this case at least, the writing system was dictated by the medium that was available to be written on. Also, if I was carving a story into a stone using the tools available 3,000 years ago, I might be inclined to use the most efficient means possible, which would be logographic or pictographic over letters. And, TBH, pictograms seem to be a natural way to start a writing system, and I can see how they would evolve to logographic systems and letters as the available materials changed and as people tinkered with them.
