Answer:
Before the invention of braille, there was not a reliable independent means of writing for blind people. If a blind person needed something written, it would be dictated to a sighted scribe. Books for the blind were created using embossed print letters. These books were very large and expensive to produce. Reading embossed print letters is a slow and difficult process. Embossed print letters are optimized for recognition by sighted eyes moving across a page, but are difficult to distinguish using fingers brushing across the page. Each letter must be traced individually with the fingers, which is slow and prone to errors.
Braille is optimized for how the brain perceived changes in texture, so the symbols can be smaller and can be read faster and with fewer errors. Braille can be written independently by blind people with a kind of stencil called a slate, or with a braille writer (a typewriter with 7 keys that makes braille letters).