There are various reasons for that, and those reasons extend beyond leaving out vital functionality. While C is archaic by our standards, and existed at the time VisiCalc was developed, it was programmed in assembly language. It pretty much had to be, simply to hold the program and a reasonable amount of data in memory. That, in turn, meant understanding the machine: what the processor was capable of, the particular computer's memory map, how to interface with the various peripherals. You sure weren't going to be reaching for a library like curses. While it, like C, existed by the time of VisiCalc's release, it was the domain of minicomputers.
I mean, can the current generation truly understand the craft when the hard work is being done my compilers and libraries?