CSS: a:link vs just a (without the :link part)

So we're required to use the following order for CSS anchor pseudo-classes

a:link    { color: red }    
a:visited { color: blue }  
a:hover   { color: yellow } 
a:active  { color: lime }  

But my question is why bother with the a:link part? Rather, is there any advantage to the above (other than perhaps clarity) over:

a { color:red; } /* notice no :link part */
a:visited { color: blue; }
etc.,etc.