Gaming, even with the help of a well-designed controller, can be a physically demanding task. It requires coordination, skill, and hand-strength, even for the simplest first-person games. Not everyone has that strength.
Video games can be particularly difficult for those with physical disabilities. Thankfully, industrious makers are always coming up with new ways to help disabled gamers play with ease. We've seen plenty of cool solutions over the years, from duct tape to wheelchair mods.