I used to think they were entirely useless, but since then I've learned of many instances where a much better technology is developed because the first iteration is patented.

For example, the Wright brothers biggest contribution to aviation was suing everyone using wing warping (https://en.wikipedia.org/wiki/Wright_brothers_patent_war) which greatly advanced the adoption of the much more advanced ailerons.

Software patents have a similar effect, for example Cisco's patent on Virtual Router Redundancy Protocol led to the development of the more secure and more capable Common Address Redundancy Protocol (https://jacobfilipp.com/DrDobbs/articles/SA/v14/i05/a6.htm).

We tend to invest heavily in whatever we can get working first, but it's rarely close to an ideal way of doing something. By pushing every developer to find a newer, better way of doing something, patents prevent stagnation and lead to more advanced technologies.

This sort of benefit in software can be realized with much shorter terms. A 5 or 10 year term would accomplish pretty much all the same benefits. 25 years is just way too long for software.