Why do people say building your own pc is better it seems like to much of a hle?

okay so everyone sais building your own pc is better and cheaper but when i go to newegg.com no motherboard has 5 stars and when i read the reviews theres always something wrong with it. it just seems like building one yourself is a hle and when you buy one from alienware or falcon northwest etc they come with the exact parts you can choose from so you know itll work rather than choosing parts yourself and then keep switching and returning them for something better. my theory is there shouldnt really be a better or worse,just something "just right" for whatever pc your building and i think thats what companies offer rather than building yourself.