Of course it is to encourage innovation
During the patent protection period, the patent holder has absolute monopoly rights over the patented content; after the patent expires, anyone is free to Restrictions on the use of technology described in patents.
So, the longer the patent protection period, the greater the benefits that inventors get from it, and the more incentive they can invest in research and development. At the same time, correspondingly, the longer this monopoly exists, the more additional losses it will cause.
So: the benefit of a long patent term is to encourage innovation, and the cost is to encourage monopoly.
Using microeconomic theory, we can conclude that when these two conflicting results are balanced, it is the optimal patent term.
Many scholars internationally have indeed studied this issue, as to how long a patent term can encourage innovation while preventing additional losses caused by monopoly. But this problem is also very complex because it involves many unknown variables and relationships. But we can estimate it with some simple calculations. For example, the patent term in the United States is 17 years, which has been calculated by some American scholars to have an efficiency of 90%.
In short, intellectual property protection based on the patent system encourages innovation, but it must be considered that patents have three dimensions: length, width and height. The length is the time of patent protection, the width is the scope of explaining the content of the patent, and the height is the standard for establishing the novelty of the patent. Unfortunately, it seems that only the length of the patent can be easily quantified. It has also led to a large number of companies applying for patents indiscriminately, resulting in lower patent quality.