A sea-port city like Athens was very rich, as it dealt with traders from all over the world. This not only meant being in contact with all types of creeds, morals, traditions, etc., but also, foreigners with pockets full of money and ready to incur in all kinds of vices.
On the other hand, Spartans frowned upon having personal wealth. Also, they were xenophobes of the strongest type and multiculturalism was not their strength ;)
Upon seeing the effect that precious metals as currency and otherwise would cause in people and civilizations, Lycurgus, a Spartan lawgiver, implemented a provision that prohibited the circulation of such metals in their territory.
Taking this measure was like killing 2 birds with one stone: a) Contact with + contamination by other cultures was greatly diminished [as there wasn’t much desire for trade with Sparta, whose economy was mostly based on agricultural production aimed at their own needs].
b) Bribery and other unwanted money-related behavior were also greatly eliminated.
When did Sparta begin to fall?
Well, you guessed it! It was when gold currency was reinstated. Then, they began to forget their old ways and became more flexible toward foreign influence.