Knowing more languages broadens ones horizon and enables one to read foreign literature without translation losses.
This is only true if you're more fluent in said foreign language than the translator, which probably isn't the case. And it only works for one language. Six years of studying French for several hours a week doesn't help you read Dostoyevsky or Kafka without translation losses.
I hated French lessons with a passion, but 12 years later I was in Belgium at the customer site and noone there could speak any of the three languages I am fluent in. My broken French, on the other hand, was sufficiently understandable for them.
Do you feel 4 to 6 years of taking French classes were a good investment of your time because of this one incident 12 years later? I certainly don't. Give me back those wasted years.
Dostoyevsky wrote in Russian, and Kafka in German, so those French lessons wouldn't help anyway. Better examples would be Albert Camus or Marcel Proust.
"Take that, you hostile sons-of-bitches!" -- James Coburn, in the finale of _The_President's_Analyst_