That's sort of how Windows quick startup works. It saves the kernel state after startup, and on next startup, it restores it (kind of like hibernating the system). Iirc emacs does something similar with its lisp runtime as well.
And because the BIOS isn't your only state-holder, anything with a controller on it inside your PC holds state, and that is basically everything today. Including external devices, like everything connected via USB (actually those have two controllers minimum, a USB controller which holds communication link state and a controller for the actual device function, like being a keyboard or mouse).
It totals to hundreds of controllers, and it simply isn't feasible to standardize a way for this entire system to somehow store an overall consistent runtime state. That is why plan B is taken: just re-establish that state every time. We call this process "booting" or "initializing".