I think some GMs don't have their suspension of disbelief falter when magic is involved, because it (usually) explicitly breaks the rules of how things work in the real world; many of the 2014 background features (and other "mundane" character abilities) at least seem to operate in more real-world ways, so they get more scrutiny, so GMs see (and focus on) how they wouldn't work, so they don't work.Especially weird in games that seem to express the idea that all the PCs, spellcasters and non-spellcasters, have unique, nearly mythical abilities but some DMs only give magic spells a free pass but “mundane” abilities more scrutiny and required fictional buy-in.
I think this is closely related to what I've seen called the "guy at the gym" fallacy.