Because a line or phrase catches in our craw. Because our zeal for poetry in another language sweeps us away. Because we’re addicted to pursuits that garner the least amount of money and fame. As W. S. Merwin once said, all translation is impossible, yet we seem to need it just the same.
For these and other answers to the question of why poets translate, take a look at the most recent installment of my column on new poetry in translation in the May/June issue of the American Poetry Review, which includes a discussion of Merwin’s Selected Translations: 1948-2011, David Wevill’s Collected Translations, and my most cherished book of poetry translation of all time, Ghazal’s of Ghalib.