Empty Sequence Shortcut?

Is there any reason why we can't have:

<p:input port="parameters"/>

as a shorthand for:

<p:input port="parameters"><p:empty/></p:input>

-- 
--Alex Milowski
"The excellence of grammar as a guide is proportional to the paucity of the
inflexions, i.e. to the degree of analysis effected by the language
considered."

Bertrand Russell in a footnote of Principles of Mathematics