Reading out loud was a social activity for many centuries and only recently did it become a silent, solo activity.
There is debate as to why silent reading started. One is because the layout of text changed to include spaces and punctuation. Others say it was the printing press that encouraged silent reading. There is also a debate as to when it started, somewhere between 1500-1800.
Reading out loud did not stop with silent reading due to the social nature of the task. People would take turns sharing passages while doing every day tasks. It was also encouraged to ensure young people were not corrupted by writers like Shakespeare.
Starting in 1865, Cuban cigar factory workers hire a lector to read books to them while they work and it still continues today. The leftist bent of the books caused a strike in 1931. Montecristo cigars company is named after the Count of Monte Cristo by Dumas, which was read in the factory, and the logo depicts swords which is in reference to the book.