Do You Really Need Immutable Data?

Immutable state has been all the rage for the past few years or decades. The multithreaded multiprocessing future is coming! Save yourselves and your sanity, use immutable data! Be functional! Object-oriented is for dinosaurs. 
This push has been particularly strong and revered in JavaScript land. Everyone got tired of messing around with jQuery, so now we’re doing immutable everything with fancy-pants unidirectional architectures.