Can’t understand why Li need to be in caps can, can anyone explain?

function toggleClassDoneOnAndOff(event) {
    if (event.target.tagName === "LI") {
        event.target.classList.toggle("done");
    }
}
ul.addEventListener("click", toggleClassDoneOnAndOff);

Can anyone explain why LI need to be in caps?

I just try to find the answer but dont understand the explanation