I wonder how it can apply to an individual - say I am developing a feature at my job today. Five years later, I am on a different job, but developing a similar

I wonder how it can apply to an individual - say I am developing a feature at my job today. Five years later, I am on a different job, but developing a similar feature for some other employer. I wonder how much of the two implementations that are apart by 5 years but done by the same person, would be similar (even after accounting for my own personal growth in terms of programming abilities)? What if I am a teacher who is creating quizzes and exercises? Or a graphic artist making illustrations from eerily similar requirements? I suppose this is an interesting question, not quite black and white? That said, don't these huge companies have armies of lawyers to protect their IP?