You don't have to, of course, but if you think new clothes from the store are spotless, you'll probably be disappointed...
Clothes are touched by many hands in the store and tried on by different people. Each and every one of them leaves bacteria behind on the garment.
Read also: '5 tips to keep the white laundry white'
Some bacteria are dead after minutes, while others can survive for up to six months. You don't want to risk getting an infection, so it's wiser to wash new clothes before wearing them.
In addition, garments may contain chemicals from the factory, which can cause itchiness or rashes if you have sensitive skin. Anyway, put those new clothes in the laundry basket.