Speed

Faster is better?
Who cares about speed if it is not secure

"The UNIX Time Sharing System" by Ritchie and Thompson in 1974:
"Early versions of the operating system were written in assembly language, but during the summer of 1973, it was rewritten in C. The size of the new system is about one third greater than the old. Since the new system is not only easier to understand and to modify but also includes many functional improvements . . . we consider this increase in size quite acceptable."

Not yet been optimized
Not even profiled