Why do most keyboards feature a QWERTY layout?

The QWERTY keyboard layout was popular on early mass-produced typewriters, and its continued use is the result of its early success. While people have developed a number of alternative layouts over the years, the QWERTY layout's ubiquity continues.

The exact origin of the QWERTY layout is unclear. Some attribute its design to efforts to keep arms on early typewriters from striking each other and jamming the machine, while others argue that the design evolved from telegraph operators. Regardless, QWERTY's early success proved to be a major reason why other designs have failed to match its popularity, despite the move from mechanical typewriter to electronic keyboard.