Always have protection when in bed, you never know what will happen
It is recommended by the National Sleep Foundation that adults should get 7-9 hours of sleep each night, and children needing more. Since your mattress is going to be used for at least 7 hours each night, why would you not want to keep it fresh and protected?
The best way to make sure that the mattress you spend so much time on stays in “like new” condition is to equip it with the best mattress cover you can find. These covers help to protect against moisture, mildew, sweat, accidental bedwetting, can be hypoallergenic and can aid in reducing symptoms of eczema, asthma, and severe allergies, especially to dust mites.
Body fluids such as sweat is very acidic and brakes down the mattress faster then just about anything. So as much as it protects the looks of the mattress, it also helps the mattress last longer. The health benefits are important as well.