Not all data structures are a large balanced tree and a O(1) update is going to be faster than O(log n) updates. There is still going to be a significant performance hit from having to recreate a whole node instead of just updating a single value. While yes you can say large data structures are like a big node of a tree, having to copy all of the different records from the old one to a new one is going to be considerably slower than just modifying a single record.

It does help, but it's still going to be significantly slower than just modifying a single record in a data structure. It is a still a problem that will be slowing down your program.