The entire Y2K problem was from tens of thousands of programmers arbitrarily taking short cuts in their programming
I suspect you're relatively young as there were valid reasons to only store 2 digits for the year.
The problem started because on both mainframe computers and later personal computers, storage was expensive, from as low as $10 per kilobyte, to in many cases as much as or even more than US$100 per kilobyte. It was therefore very important for programmers to reduce usage. Since programs could simply prefix "19" to the year of a date, most programs internally used, or stored on disc or tape, data files where the date format was six digits, in the form MMDDYY, MM as two digits for the month, DD as two digits for the day, and YY as two digits for the year. As space on disc and tape was also expensive, this also saved money by reducing the size of stored data files and data bases.
And early then that you had to deal with punchcards, which could only store 80 characters per card. Punch cards were still in use when I went to college at Del Mar in Corpus Christi in 1984. While my incoming class was the first to no longer use them as part of our curriculum, the older students still used them. Everybody also used them during the registration process - pick up the card with your name on it at the entrance, walk around to the tables set up for each department and get a punch card for the class you wanted (if they were out of cards the class was full), then turn in the stack of cards to complete your registration.