Most of what we think we know about Spartan culture and practices was written by their enemies, or at least by people unsympathetic to Sparta. They left very little written records themselves.
Oddly enough, many of those Athenians who wrote about the Spartans had great admiration for them in many ways. Xenephon is a good example, but the sentiment was widespread among writers of conservative bent.
Spartans were often viewed as sticking to the old ways while other Greeks, especially the Athenians, had become effeminate and corrupt.