[codyjones]

It's likely the Firefox developers use more of its shortcuts because they are more familiar with the product and are more interested in optimizing their workflow than a typical user. Exploring, which includes backtracking, is the core of the web browsing experience so I'm not surprised people are doing that far more than, say, searching for a substring.

It's also worth pointing out there isn't a great opportunity to learn the keyboard shortcuts Firefox provides. Traditionally you'd learn shortcuts by seeing them next to menu items, but the menus are hidden behind the Alt key, and many actions simply aren't listed there. For example, "Find Again" / F3 is omitted.