Can someone explain why or for what purpose you would create a "phased" kit?

Having tested my mother and me and loaded the results into Gedmatch, I did the phasing, but do not know what to do with the results. And now I have my paternal uncle and my paternal grandmother tested and loaded. I could create another phased result but do not know if it is worth the effort.

For the record, the genetic information I am most interested in is what came from my paternal grandfather (deceased). Since my father is also deceased my paternal uncle was his "stand-in" for testing as the closest relative. I have received valuable YDNA data from him giving me strong clues as to my paternal great-grandfathers birth family.

Thank you!
Elizabeth