It can still be non-obvious with an optimizing compiler, or with non-Lisp.

I don't see the point in having beginning students think about tail call optimized recursion vs normal recursion unless they're going through SICP. In the end it can totally be a compiler thing. For instance, GCC can optimize this:

    int factorial(int x) {
       if (x > 1) return x * factorial(x-1);
       else return 1;
    }

into this:

    int factorial(int x) {
       int result = 1;
       while (x > 1) result *= x--;
       return result;
    }

(http://ridiculousfish.com/blog/posts/will-it-optimize.html)