Who said they make a very small change? I said they improve a single aspect. The aspects are normally massively changed.
And the point people are making is they can't spot the differnce and for them there is no difference. No there is, but they're not good enough to feel or see the difference. It's like saying there isn't a difference between each version release of a programming language. If you're a newbie programmer you won't notice the difference but if you're an advance user you notice it instantly and it changes how you do things.
One of the reasons I normally upgrade every year is that I found if I missed a year the number of changes that I would experience with basically overload me when I did upgrade.