After all, every single byte is precious when you have so few. And that's one of the reasons programmers begin storing dates as six digits of information. When we see a data like 012450, we all know what it means. Winchester invents the hard disk. Intel comes up with things like transistors and integrated circuits.
Computers gradually get smaller, more powerful, less expensive.
The PC is born in the late seventies and legitimatized by IBM in the early eighties. By the nineties, they've become commodity items, with prices driven lower and lower by volume merchandising. And still programmers and data entry people are storing dates as six digits, dropping the century as wasteful and unnecessary. Because, after all, that's the way it's always been done . . . Today Computers didn't just become smaller, more powerful, and less expensive.