Yes, but drills of that sort are so time consuming that many players simply don't have that kind of time to invest, or they just don't want to work that hard. So they look for systems that might help speed up their skill development when it comes to pocketing balls or playing position or kicking or whatever. The alternative is to solely rely on experience. And, unless you have no job and pool is your only interest, your experience is not likely to be all that rewarding.
It all boils down to training the mind through deliberate practice and repetition. A good system can help with that training. And "good" is a matter of personal preference and personal experience. In other words, a system I find useful or helpful could very well be useless crap to someone else. And that's fine.
When you're trying to improve or learn any skill, you have to navigate through a sea of learning options to find what works best for you, because YOU are the sole captain of your ship.