It depends on how you define "need."
Required by the regs? No. Essential for learning the ins and outs of Instrument flight and Commercial maneuvers? Not really. An aid to safety? Sure, as long as you don't depend upon it as your sole means of separation.
I find it useful even when just bumping around the pattern. If you're using ForeFlight, you've got the Scout as a low cost alternative to some of the other ADS-B In options.