Fifteen years ago every piece of hardware supported windows and windows was arguably more friendly for casual developers than Linux with things like Visual Basic and Delphi so a lot of novel and very custom software was written (guilty as charged). The good thing is that most of these still work, as windows has thankfully not fucked with the underlying Win32 libraries. The bad thing is that this one piece of custom software was probably written by someone of retirement age and it is probably what's running the company.

This is just life, the same will happen to your latest wiz-bang program you wrote today in ten or fifteen years, good companies insist on the source code and/or plan for obsolescence, others become cash cows for the software industry or die.