[eknkc]

Why is it optional? What is the benefit of having it disabled by default if there is a decent implementation?

[anonova]

They disabled it for error reporting/debugging reasons. Because you don't need to create a new stack frame, you eliminate that information in the backtrace.

[steveklabnik]

I've seen at least one paper that shows a way to fix this... hm.

[Tuna-Fish]

A lot of people prefer having complete, explicit stacks for debugger use over having tail calls.

[hajile]

loops don't leave a stack trace either...