Again, I believe the New 52 doesn't have the cape as part of the Kryptonioan armor but is, infact a "baby blanket" from the spacecraft that Superman has somehow incorporated into his uniform. (Giving it the nano-properties of the suit so it can shrink/disappear as needed. Superman has sort of a Linus-ian attachment to it.) So while the cape isn't part of the battle armor it's still a Kryptonian material and just as "indestructible" as Superman's suit.
Also in the New 52 Supergirl was sent to Earth in suspended animation wearing ceremonial coming of age/graduation clothing (or something like that) that DID include a cape and is of a design that says a lot about gender roles on Krypton.
I've never much liked the idea of Martha Kent making the suit out of the blankets/upholstery of the Kryptonian spacecraft simply because unless the spacecraft also came with Kryptonian sewing equipment she'd have a hard time cutting and sewing the cloth.
I think I prefer the idea of it being some-sort-of Kryptonian garb that Superman simply dons as a suit. It's design simply resembles earth ideas on "superhero costumes." I mean, that makes as much sense as the family crest for the house of El happening to look like the letter "S" (for Superman.
) in the Latin alphabet.