This question is an artifact of not really deeply understanding Javascript. Yes, your jQuery loop looks different than the Javascript loop you might "normally" write... but it doesn't look all that different from my Javascript code that I was writing before jQuery was even a glint in Resig's eye.
jQuery uses Javascript more deeply than what you get out of a "Learn Javascript in Ten Minutes!" tutorial, but it's still just using the language. It is a library, not a language. If Javascript didn't have closure support, jQuery would be up a creek without a paddle. (We all would; without that feature JS programming would be an order of magnitude more nightmarish.)
And if you don't understand how it is using the language, you will not be able to use jQuery to its full advantage. There's no substitute for understanding.
jQuery uses Javascript more deeply than what you get out of a "Learn Javascript in Ten Minutes!" tutorial, but it's still just using the language. It is a library, not a language. If Javascript didn't have closure support, jQuery would be up a creek without a paddle. (We all would; without that feature JS programming would be an order of magnitude more nightmarish.)
And if you don't understand how it is using the language, you will not be able to use jQuery to its full advantage. There's no substitute for understanding.