Why does someone get cancer? Why does someone get hit by a drunk driver? Why does Donald Trump have a gazillion dollars while hardworking people are unemployed?
Life isn't always "fair." Sometimes things (good AND bad) happen seemingly randomly.
What counts is how you respond to what life hands you. This is also known as "living life on life's terms." It's a good expression to keep in mind as you begin to navigate life sober. The world doesn't "owe" you anything. It is your job to be responsible for managing this condition that you never asked for, just as a diabetic is responsible for managing his/her disease.
Actually, when you compare alcoholism to a lot of other life situations, we don't have much to complain about. Not only is alcoholism very, very treatable, but the treatment/recovery work that we do can make us better people than we would have been if we had never encountered this particular problem.