NIST has a total of 3 approved block ciphers on their website: AES, TDES and skipjack.
I get why those are on there (though personally I find TDES a bit iffy) but from my understanding Twofish and Serpent are also good enough to make the list. so why aren't they there? are they too weak? have they been broken to an extend where they are no longer safe to use?
I'm really interested in knowing why some ciphers are recommended and others aren't. I'm looking for an algorithm to use my self, to do this I want to make a selection of a few algorithms which are safe to use so I have a reason to fall back on when i'm asked why i chose for that specific cipher other than the standard excuse because it's AES (or NIST approved)
Are there credible sources I could quote for other algorithms (such as Twofish) which shows they are still reliable?