A huge difference between 1995 and today is in 1995 "simcity.exe" might represent fewer than a half dozen artifacts because patches and updates were rare. An exception covering a handful of cases is maintainable and testable.
Today patches are near constant so a "simcity.exe" might represent hundreds of different versions of the code. It's much harder to maintain exceptions since the list of cases is much larger. Even if your test harness is embarrassingly parallel your results are only as accurate as the latest version available to test.
None of that is impossible but there's additional non-zero costs involved in maintaining compatibility exceptions. At some point they tip over to not being worth the investment.
Today patches are near constant so a "simcity.exe" might represent hundreds of different versions of the code. It's much harder to maintain exceptions since the list of cases is much larger. Even if your test harness is embarrassingly parallel your results are only as accurate as the latest version available to test.
None of that is impossible but there's additional non-zero costs involved in maintaining compatibility exceptions. At some point they tip over to not being worth the investment.