Changing up your food

I always see/hear people talking about how you should change up what you eat from day to day because your body can get used to what you're eating. I really don't understand that. If you are eating your macros and eating healthy things like fruits, veggies, lean meats, etc. why do you have to change it up, if not just out of pure boredom? I'm just curious because I'm a college student who is doing an internship right now PLUS taking classes and it is so much easier for me to eat the same thing every day and pack it in containers the night before than experiment with new recipes and change up what I eat.