In 77 a laundry room sink was not required to be GFI protected. So, the one in place may have had the outlet/protection added at some point. Is the one that is not GFI the 110 volt outlet for the washing machine? If so, those often aren't GFI protected even in new construction, at least not in my area.

The root of your question is really how far down the road of suggesting/recommending/requiring an older house be updated to the standard of a newer house?

Here is the comment I paste into my reports...

GFI protection is recommended in all wet locations (kitchen, bathroom, exterior and garage). This feature was not common when the house was built but is a recommended safety upgrade given the potential hazard of using electricity around water.

The GFI thing is particularly tricky when it comes to old houses vs new. There have been a lot of changes in the code over the years, thus a lot of different recommendations. That is why I choose to go fairly general.

Others will likely chime in with some different approaches... the above method has worked for me but is in no way the only way.