traceback() for interactive and non-interactive R sessions

I observed a different between an interactive and non-interaction R session about traceback() which I do not understand. For the code below, it will produce an error, but in an interactive R session, I can see the traceback information, whereas if I save the code to test.R and call it via Rscript test.R or R -f test.R, I can no longer see the traceback:

f = function() {
  on.exit(traceback())
  1 + 'a'
}
f()

In an interactive R session:

> f = function() {
+   on.exit(traceback())
+   1 + 'a'
+ }
> f()
Error in 1 + "a" : non-numeric argument to binary operator
1: f()

Non-interactive execution:

$ Rscript test.R 
Error in 1 + "a" : non-numeric argument to binary operator
Calls: f
No traceback available 
Execution halted

I did not see an explanation in ?traceback, and I'm wondering if there is a way to enable traceback for non-interactive R sessions. Thanks!