Aiming systems, regardless of which one you use, are about creating a consistent repeatable pre-shot routine. You have to back up any aiming system with solid fundamentals, that is a given. The greatest of players (those that have already HAMB and are very comfortable with their ball pocketing) may have no use for a system to change what they already do very well.
Eventually, aiming systems help a player fall into a procedure of subconscious movements. Shot recall will take your conscious mind to other parts of the shot, and make shot making itself much more automatic. HAMB is a system! Don’t forget that. It is just that some systems are more efficient than others for different people.
If we address a system known as CTE/Pro1, it starts with a very discreet system of movements using pivots. Eventually (moving to Pro1) it replaces manual pivots with eye movements. HAMB is a system that also works. You shoot and shoot and shoot until you can pocket balls without thinking. Aiming systems try to reduce the amount of effort to reach this goal. Each approach may work differently for different people.
IMHO that is the purpose of aiming systems, to minimize the journey to subconscious ball pocketing. Some like HAMB/PIITH/ROTE, some like fractional aiming, some like stick aiming, some like pivots. There is no argument here, it’s just how you want to take the journey to ball pocketing proficiency. They all lead to the same place, but some are easier/better/faster for different players.