When an immune system malfunctions, pathogens grow in larger numbers causing more symptoms more conditions more agony and more suffering.
In this day and age it's imperative that your immune system is functioning properly.
Every single body function relies on your immune cells – without them we would be trapped in a bubble with purified air pouring into it unable to leave that bubble and partake in life.
That's how critical our immune system is for survival here on earth.