It's not about "having" or "not having" keys for specific actions, it's all about freedom and feeling of control. When you take and apply the idea of modality, you quickly realize that you are no longer constrained with the number of combinations you can have or the type of keyboard you're using. Everything can be controlled by (mostly) using home-row keys - h/j/k/l - without having to memorize weird combinations of modifiers and keys - "was it Ctrl+Alt+Cmd F, or just Ctrl+Cmd F?"
alt+cmd (was a typo, I meant to say alt+space), which is configurable - I myself prefer using cmd+space. That opens the "main" modal, from where you can configure "conditional branching" - e.g. "m" - for "media", or "a" - for "apps", so with "alt+space m j/k" you can do volume up/down, while pressing h/l could be "previous/next song". Then, "alt+spc a b" activates the browser, and "alt+spc a t" - could be bind to activate "terminal", etc.
It only looks like you have to press more keys to achieve anything, in practice - you quickly develop muscle memory. Then switching between the apps, moving windows around and resizing them, controlling playback, etc. - it all gains incredible productivity without affecting the focus point. You don't need to keep moving your hand for the mouse, you don't need to memorize and deal with myriad of modifier-driven key combinations - you control precisely what you need, without ever having to contort your fingers to hold modifiers, without ever thinking "what should I bind this action to, all memoizable keys are already taken, I suppose I'll just bind it to this impossible combo with a key that has no semantic meaning for the thing..." With Spacehammer you can create mnemonically-handy actions e.g., "o f" for "Open in Finder", while in another context that may work as "Open in Firefox".