Actually, as I understand it (never having actually read this in a comic), the alternative was that Superman’s invulnerability forms an aura that extends maybe half an inch outside his skin. Consequently, his tights were protected, but his cape could get torn up in action.
The Spectre has been working that look since 1940.
The original explanation was the super-blankets. When John Byrne did his “Man of Steel” mini-series in the mid-80s, one of the things he retconned was changing the blanket explanation into the aura. IIRC the aura was art of Superman’s invulnerability and also protected people he carried while flying from friction. This was part of Byrne’s overall attempt to move Superman’s powers from the realm of the physical to the psionic. I believe that the aura has been retconned back into the blankets, along with most of the other Byrne-era retcons.