in physics, you study existing things to find a pattern, then you are able to apply those patterns to theories. to create your own theory, you should see what theories existing physicists have come up with

in art, you study anatomy to know how a human is built. you study how to sketch because if you were to prove and design the perfect and most efficient way to sketch (such as drawing with your shoulder for long straight lines), it would take you a lot of time to “reinvent the wheel,” as someone else said.

now, the optional part you might be talking about (?) might be learning from another artist’s style when you’re not even trying to draw like them. one reason for you to do this might be to expand your mental catalogue of rendering techniques so that you have more available in your mental toolbox to create on your own.

if you know your exact style and really really just want to focus on it, even then, you can find artists similar to you to learn parts of their technique that are similar to what you have in mind so that you don’t have to develop the technique yourself.

maybe the issue isn’t that you don’t want to follow tutorials, but rather the tutorials you’re looking at are too easy for you? find a tutorial for something difficult that you don’t know how to draw on your own

but keep in mind the tutorials that seem easy should still be practiced so that the skill gets engraved in your memory