From what I understand the ethanol in fuel will attack certain types of rubber, as found in fuel hoses, seals etc.
Cars built after around 1980 when ethanol was first introduced would probably have compatible fuel system components.
Based on that I suspected that there might be some percentage ethanol in regular fuel as well(but I've not been able to confirm that),
since newly installed rubber lines seem to be going bad after just a few years in use.
At least that's my experience with the original braided fuel hoses from Mercedes.
So a while ago I decided to sacrifice originality and have those hoses made with non braided modern rubber.