Here's my take on why that is. Most of the better players in the past had no formal instruction. They learned just by playing, and by a few "tips" passed on from other players. When one only learns through playing, they tend to key in on certain things that worked for them.
For example, they one day had a soft shot with a good amount of spin required. What is now known as a finesse shot. They just happened to use a light grip on it with just their fingers on the cue, and found that they were successful. So, the next time a shot like that came up, they tried it again, and were successful again.
So, to them, that shot required a different grip and different way of shooting it. A different stroke. And, they passed that on to someone along the way.
What they didn't realize, is how the balls actually "work" with everything. They didn't realize that they could have made the shot with the same results using a standard way of shooting, and only varying the force behind the shot.
Today, much more is known about ball reaction and all the rest that goes into a good stroke. One of the things that we have learned, is that there is a way to play without having all the gadgets and bells and whistles that some think are dark, hidden secrets that only a few know about. While a lot of that "stuff" may work, it really isn't necessary and only adds to what can go wrong.
Or...they tried shooting the shot many times with their standard way of shooting but with less force & never got the complete result that they wanted, so...they tried it a different way & found success.
Each individual reader can make their own determination as to which seems more logical & makes more sense.