There are so many practices weight lifters accept as fact. 5-7 reps for power lifters/8-12 for hypertrophy/13+ for endurance, working out for the pump, eccentric motion is where the muscles break down, too much cortisol after 40 minutes of lifting to do any good . Some of these are disputed here and there but generally 80-90% of lifters assume they are the only way to train. However, a workout plan with bodypart splits, such that each bodypart is trained once a week directly, is probably the most mainstream idea of them all.
While most bodybuilding begins with whole body workouts, it doesn’t take long before you read that you are going to get to a point where you can’t sustain 3 days a week of full body workouts. The reasons given? The loads you are using are going to be too high to recover quickly enough, the amount of sets per bodypart required for continued growth are too high and would take too long to train a full body workout, etc. These all seem like great reasons and we all go along with the plan. We start training back and biceps one day per week, chest and triceps another day, legs still another, etc.