Why can't strings be mutable in Java and .NET?

Why can't strings be mutable in Java and .NET?

java .net string mutable

java

Is Integer Immutable

java immutability mutable

java

Create mutable List from array?

java arrays list mutable

java

Does Java have mutable types for Integer, Float, Double, Long?

java numbers integer mutable built-in

java

What is difference between mutable and immutable String in java

java string immutability mutable stringbuffer

java