Why only literal strings saved in the intern pool by default?

Question

Why by default only literal strings are saved in the intern pool?

Example from MSDN:

String s1 = \"MyTest\";
String s2 = new StringBuilder().Append(\         


        

Answer 1

The language designers decided the cost of interning every intermediate string value was not worth the performance cost. Interning of garbage-collectible strings requires a single global weak map which can become a bottleneck when you have large numbers of threads.