Why would you need the "S" power in Contra or an M4 rifle in Counter-Strike when you have the default weapons?
Though you will be able to achieve the ultimate goal of killing the opponent even with the basic tools given to you, usage of those specialized tools facilitate the ease of achieving the said goal, that's why.
Similarly these functions that we are about to learn are going to provide us with easy ways of controlling Git to provide data according to the various situations which you can decide where it fits in, based on your job role. And moreover, it's fun to have some ready-made tricks in your pocket to pull out when the need arises, making you the apt person for the job.