Why do Torah scrolls not have vowels or Trope, thus forcing the reader to memorize both?
Is there a historical or Halachic reason for this?
The vowels and cantillations are part of the Oral Torah, and were thus to be memorized and transmitted from generation to generation. Only when we (relatively recently) began writing down the Oral Torah, did we also invent ways to write vowels and cantillations. However, not to add anything to the Holy Torah, we do not write them into Torah Scrolls, only into printed books, like a Tikkun (a special version of the Torah Scroll designed to aid memorization).