Supposedly Waterproof Nike "Shield" Raincoat Allows Water In

I purchased a supposedly waterproof "Shield" raincoat, advertised as both waterproof and water repellent. However, the raincoat ended up allowing water to seep through the shoulder seams. How is it that a product with these supposed features lets water in? Are we paying extra for this brand in vain? I am utterly dismayed and disappointed, having lost trust in this well-known brand. Just look at the regretful state I'm now in.... I will never choose Nike again, as this experience has left me profoundly disillusioned.