It is more likely that there are no relationships involved in the design at all.

This. Lots and lots of the time the table creators were apparently thinking 'flat file.' This probably has a lot to do with access being the entry point for talented amateurs to get into programming, ie

1. a company needs something done,

2. looks around the staff for someone with some ability,

3. said someone develops an app that works,

4. the app starts to be used,

5. now the company's stuck and can't get out of it