Gray waterproof knitted fabric has a number of advantages, including:
Waterproofing: The fabric is treated with a waterproof coating or membrane, which makes it resistant to water penetration, keeping the wearer dry in wet weather.
Breathability: The knitted construction of the fabric allows for better breathability compared to a non-knit fabric, which means it will help to wick away moisture and sweat from the body.

Durability: The knitted construction of the fabric makes it more durable than a non-knit fabric, and less likely to tear or rip.
Stretchability: The knit structure of the fabric allows for it to have more stretch and movement, providing a greater level of comfort for the wearer.
Lightweight: Due to the knitted structure, it can be made in lightweight but still waterproof and breathable fabrics.
Gray color, can be combined with other colors, and it's quite popular color as well.