Yes and no ;)
A mouse user 'may not' need a skip nav link.
A keyboard user will usually like the option of not pressing the tab X# times.
Why hide? well design reasons may be one, not confusing non-keyboard users another.
Mouse user clicks on skip nav and nothing happened, well yes that's because the design has all the nav links horizontal. So lets hide it from them.
Text browser, or css disabled, up pops a handy skip nav link.
but what about a keyboard user who has css enabled?
Well as soon as the skip nav gets focus up it pops and offers a little help.