Maybe the input is case insensitive, for example if you work with html you might see "DIV","div" who knows some crazy dev or tool might generate "DIv" or "dIv"

Maybe the input is case insensitive, for example if you work with html you might see "DIV","div" who knows some crazy dev or tool might generate "DIv" or "dIv" so is simpler to lowercase the input then work on it.