I just edited your post to make thing more readable,
CSS can be coded different ways and one of the ways is using shorthand, lets look at your firse bit of CSS which is
HTML Code:
div#menu1 ul.rMenu li.current-menu-item a:link,
div#menu1 ul.rMenu li.current-menu-item a:active,
div#menu1 ul.rMenu li.current-menu-item a:hover,
div#menu1 ul.rMenu li.current-menu-item a:visited,
div#menu1 ul.rMenu li.current_page_item a:link,
div#menu1 ul.rMenu li.current_page_item a:active,
div#menu1 ul.rMenu li.current_page_item a:hover,
div#menu1 ul.rMenu li.current_page_item a:visited,
div#menu1 ul.rMenu li a:hover {
color: #F4F4F4;
}
wow that is a lot of CSS selectors, you could have each one like this
HTML Code:
div#menu1 ul.rMenu li.current-menu-item a:link {
color: #F4F4F4;
}
div#menu1 ul.rMenu li.current-menu-item a:active {
color: #F4F4F4;
}
etc...
but since they are all setting the color to the same thing, putting them all in one statement means you can make one change and it will apply to them all.
Now for a history lesson. Prior to WP release 3, themes had to deal with menus themselves. Atahualpa use a menu scheme called 'Ruthsarian's rMenu' (you can read about it at
http://webhost.bridgew.edu/etribou/layouts/) which is where the class 'rMenu' and 'current_page_item' or 'current_cat_item' comes from. Since the theme had two menues (for pages and one for categories) the ID's 'menu1' and 'menu2' were used
Now comes WP 3 and it's new custom menu's and guess what - new class names like 'current-menu-item'. If someone used the new custom menu, then the Atahualpa menu styling nolonger worked. If the them had just been re-written so that it used the same names as WP used, you would have half the menu CSS..BUT (there always seems to be a but) then anyone who had added CSS Inserts styling theie menus different would suddenly have their site looking wrong.
So the solution was to use booth sets of CSS selectors to apply the rule.
probably more than you wanted to know, but now you may understand the 'Why is it like that' question.