What's the point of passing parameter by value (vs. const ref)

Hi all.

When writing new C++ code, what is the point of passing any (input)
parameter by value when passing by const reference will just work as
well? (Even and especially PODs, I would not do it with a complex type
anyway.)
(Given that in 90% of the code you will never want to modify the
parameter anyway.)

br,
Martin

[EXAMPLE_CODE]
class foo {
};

void f_val_int(int);
void f_ref_int(const int&);
void f_val_foo(foo);
void f_ref_foo(const foo&);

int main(int,)
{
  double d = 1.2;
  f_val_int(d);
  f_ref_int(d);
  f_val_int(1.4);
  f_ref_int(1.5);

  foo x;
  f_val_foo(x);
  f_ref_foo(x);
  f_val_foo(foo());
  f_ref_foo(foo());

  return 0;
};

void f_val_int(const int x) {
  int y = x;
  y++;
}

void f_ref_int(const int& x) {
  int y = x;
  y++;
}

void f_val_foo(const foo f) {
  foo ff = f;
  ff;
}

void f_ref_foo(const foo& f) {
  foo ff = f;
  ff;
}
[/EXAMPLE_CODE]

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