Whether you need to burn some calories or want some motivations for higher achievements it will make your purpose measurable in some way. For example, you make target for yourself that you want to maintain speed over 14 and ride 25 miles or you want to show your mates how crazily fast you were riding.
In addition, this little computer can sometimes identify if you are training too hard, you need more rest or may have to hydrate better. It will perfectly assist you in tracking your performance and your body functioning.
Though many cyclists are using smartphones for to tracking their rides I prefer this little computer help as it has more functions and it is handier to use.