Why sampling rate is not an option with normalized frequency in Matlab Filter Designer
...the normalized frequency mapped $[0,\pi]$ to $[0,1]$...


The normalized frequency $F$ is defined as $f/f_s$ where $f$ is the "real" frequency (i.e. not the normalized one) and $f_s$ is the sampling frequency. The map is thus from $[0, f_s]$ to $[0, 1]$ (or to $[0, 2\pi]$ in normalized pulsation $\Omega = 2\pi F$). When using normalized frequency $F$, you thus specify frequencies as a percentage of the sampling frequency. Hence, the sampling frequency itself is not directly needed.