Grip strength is important not only strength training but also because it affects mortality. Lifting heavy is one of the way to improve grip.
Why Your Grip Strength Matters, and How to Improve It - The New York Times
Grip strength: Unlocking Your Grip Strength: Conquering Life's Challenges - FasterCapital
The Do's And Don'ts Of Fat-Grip Training
The problem with a strong grip – GolfWRX
Why you shouldn't ignore declining grip strength
The Importance of Grip Strength
Why Your Grip Strength Sucks (And How to Fix It)
Grip strength: what the norm is and exercises
Grip strength - Wikipedia