Genetics, poor diet, lack of direction or consistency, etc...
I tell people it's just like a career, college or anything else but it's your body you're focusing on. For the most part if you don't take it seriously then you won't get serious results
How serious a person needs to take it depends on how gifted they are genetically just like with anything else. For some it doesn't take much, for others it takes an considerable amount of dedication. It's up to the individual to figure where they fit in and adjust accordingly. We all aren't the same
If I can remember correctly op is fat as hell so he need to be worried about his own gains or losses instead of hatin on the side like a bitter broad

but that's if I'm remeberin correctly, if not disregard