Not a collective fuck-up. My Pops wrote code back in the late 50's early 60's and due to the limits of memory storage, things were kept as tight as possible. So, they allowed 2 digits for year, assuming the 19xx. Also, as he stated before he passed on, they never thought their code would still be in use 40 years later.
It's easy to take for granted now, but he showed us kids the washing machine sized hard drives that held a whopping 12MB (or something of that magnitude) on several large removable disks. Memory cost was the real culprit.