First of all it is half of your body and engines for any tasks and obstacles you encounter either in training or daily movement through life ... The point of any workout or nicely built body is the proportion and harmony of muscles, functionality and stretchability, functional strength above all. I don’t know if you knew but by training your legs or lower body you also develop your upper body. HOW? The reason for this is an increase in growth hormone and serum testosterone during serious leg training. hip thrust etc ... Exercises that activate as many muscles as possible increase oxygen consumption, and so we burn as many calories as possible, which is logical.
This is not just my research but a Norwegian proven study. Also, by exercising your legs, you burn a lot more calories, which is very important for your ultimate goal. metabolism works while you rest like HIIT training and automatically burn fat cells and diet then it doesn't have to be so strict if the training was good. and should be strong because it keeps part of our upper half in synergy with other muscles that must be neither stronger nor weaker but equally strong. It helps you to overcome stairs and various obstacles, squat over 200 kg in my case, to run or resist gravity when walking uphill etc ..
(m. gluteus maximus) flexors abductors adductors m. quadriceps femoris m. tibialis anterior ... etc. There are 14 of them which are very important, not to mention indefinitely. More coming soon