You may not have moved the right file.  For 2016, you might have a pdf file saved and also a TurboTax file (.tax2016).  You need to use the .tax2016 file and then the 2017 program should pick it up as an option to transfer when you start a new return.

Also, make sure you have the .tax2016 file on the same hard drive as the 2017 program if your computer has a split hard drive or it may not read it.

Whether its really necessary depends on the information you have in your return.  If you have like rental properties and business assets with depreciation etc, then you will want the prior year return to carryover all of that data.  But, if you don't have carryovers or information such as the above to transfer, then its not a necessary thing - it will just give you a jumpstart by pre-filling information and comparing it to last year.