Innovation

It is not necessary that design patterns should fulfill all requirements so why can't we innovate our own better solution?

Yes, innovation is necessary; and certainly, we can come up with a better design and solution or even a new design pattern. Let's take the preceding example; instead of entering a secret pin, a user can use voice recognition for authentication purposes'. It may look cool to some people, but for many it may be a security concern. Speech recognition may not work because of different accents and so on. My point here is that innovation comes at a cost. In software industry, we don't always have the privilege of time because of project timelines and other dependencies.

Design patterns are age-tested and recommended techniques to address a given problem. They not only help in solving the problem at hand, but also address various possible offshoots of the central problem. Design patterns have also evolved as per requirements and will continue to do so.