I think a lot of it comes down to the usual ignorance of what the Spartans actually did and how they lived. A lot of focus is placed on their extreme lifestyles

I think a lot of it comes down to the usual ignorance of what the Spartans actually did and how they lived. A lot of focus is placed on their extreme lifestyles while a lot less is placed on their massive community of slaves (helots) and their secret police to manage them. It's funny, since the existence of a slave population which greatly outnumbered them shaped their society and led directly to their downfall. They've also always been a very useful shibboleth for people trying to make the "Effete Athenians vs Manly Spartans" comparison.