With clothing and footware particularly making something waterproof isn't that hard. The challenge that GoreTex has managed is to make it waterproof and breathable. The advantage of breathable fabrics is that sweat can evaporate from your foot/armpits etc and pass out through the material while rain can't penetrate in through the material. If the material is not breathable then you will still end up with soggy (and very smelly) sock after a long hike just from sweat.