Why is the default tab size 8 spaces? Where does this come from and why is it that big? [closed]

From the Wikipedia article on "Tab key":

In practice, settable tab stops were rather quickly replaced with fixed tab stops, de facto standardized at every multiple of 8 characters horizontally, and every 6 lines vertically (typically one inch vertically). A printing program could easily send the necessary spaces or line feeds to move to any position wanted on a form, and this was far more reliable than the modal and non-standard methods of setting tab stops. Tab characters simply became a form of data compression.

It is unclear why the 8-character horizontal tab size was chosen, since 5 characters, a half inch in a typical printer at that time, was much more popular as a paragraph indentation.