Processes come and go! The OS doesn't have to gamble that you won't actually need all the memory you allocate, it could just be a gamble that another memory ho

Processes come and go! The OS doesn't have to gamble that you won't actually need all the memory you allocate, it could just be a gamble that another memory hogging process exits before you need to use all of your memory, or that you don't need to use all of your memory at the same time.