Why did Sir Walter Raleigh write 'The Nymph's Reply to the Shepherd'?

I am doing a thesis on Elizabethan Poets and their work on the Brevity of Life. Therefore I have studied Sir Walter Raleigh's poem, and Christopher Marlowe's poem 'The Passionate Shepherd to his Love' I do not know what you have been told about the poem, but this is what I think you need to know. SWR's poem is a reply, literally a reply, to another poem written at the same time by Christopher Marlowe called 'The Passionate Shepherd to his Love' I seriously suggest you read it if you haven't, it makes SWR's poem make alot more sense. SWR was a satyrist, and so he was looking for romantic poems to mock, and having read CM's poem, I think anyone would agree it was an easy target. So really he was simply fulfilling an obligation as a satyrist, and was also furthering his own reputation because the poem was so popular. That is how simple it is really, I cannot see any other reason, he just wanted/had to mock romantic poems and this one CM's poem came along. The only other things to note are that the poem focuses on the brevity of life (as I mentioned earlier) which means it is saying how short life is and how we should live for the moment (also referred to as Carpe Diem)