If you want to maintain the state of your gridview in your page.
i.e. if you want to use that datatable with which you are binding your gridview somewhere else in your code.. than you can save the datatable in viewstate and can get it somewhere else.
in this way that current state of your gridview is persisted in viewstate for further use.
So having a gridview with enabled view state is gud idea to handle the persistance of data.
hope that will help.
Further about viewstate you can visit.
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