Yes, but not everyone programs in a vacuum. Sooner or later they'll start using code which does have prototypes. Imagine, for example, that they start using Test::More. Those functions all have prototypes and using the leading ampersand is sure to bring them woe. Imagine, for example, typing "is" instead of "ok":
&is(some_func(3,4));
The prototype is now disabled so they don't get the compile-time failure telling them that the test function has been called incorrectly. If you're new to testing or that's buried in bunch of other tests, it can be quite difficult to figure out.