WHY PEOPLE USE LIFTING STRAPS IN THE GYM?
#1 is to help the user lift heavier weight, to push past any grip and forearm strength limitations. Example: using the straps you hang longer and work your core to failure.
#2 is so you can use a very LIGHT precision grip (confident the weights won't slip from your hands) to target and isolate smaller muscles. Example: to target the rhomboid muscles (responsible for good posture) which is buried under the much larger trapezius muscle.