Because you use single keystrokes instead of chords. Most editing actions are single keystrokes im Vim. This is especially true for complex things such as macros or command repetitions. In a way, this lends itself better to muscle memory. At times, you will do terrifically complex things in Vim without even knowing how you did them. This does not happen to me in Emacs as much.
But then again, my Emacs is growing with me and with every tweak I do it is becoming more of an extension of my mind and my particular way of working. This is not something I experienced in Vim.
Vim keys are also more composable. Emacs often rely on interactive integration (i.e: start iterative search then decide to jump into a replace with the current search) which feels less general to me.
Although I agree with your explanation I always wonder if using something like keychord in emacs could allow me to move as seemlessly around the text in emacs as in vim.
P.D.: Also something the the . command in vim is only posible due to the mode switching being an implicit start macro/end macro.
In my experience, fluidity of simple commands is not much of a problem, because muscle memory will take care of that eventually anyway.
However, C-x C-S-8 is certainly a more complex move than qq.
And the one for recording a macro to a register is even more complex. So complex in fact that I don't remember it. Hence I use those commands less often.
But the flip side is that something like occur or REPLs or magit or org-mode offer different benefits that you can not quantify in keystrokes as easily.
I guess there are different kinds of fluidity. To my mind, Vim is unmatched in low-level text manipulation fluidity. Emacs optimizes for a kind of higher level work flow fluidity.
Maybe Evil is the answer. But my brain has seemingly disparate modes for Vim and Emacs that are weirdly incompatible to each other.
Also, it helps to reimplement your favorite commands in Emacs. For example, I have M-s and M-r bound to something like f/F in Vim. Similarly, M-o and C-o act like o/O.
But then again, my Emacs is growing with me and with every tweak I do it is becoming more of an extension of my mind and my particular way of working. This is not something I experienced in Vim.