In a nutshell, the answer to why patent? is to maximize the invention’s potential. A patentable invention is not only new but useful. For that invention to actually achieve usefulness, it must be commercialized.
Commercialization takes time and money – both of which are scarce resources. In order to justify the investment of those resources, there must be a reasonable expectation of return. This expectation can be assisted (not guaranteed!) by a patent ‘fence’ that protects the entity investing in commercialization long enough to realize a return on the investment.
Ultimately, everybody should win. The inventor and the ‘commercializer’ receive a return on their investment – and likely invest at least some of that return in further inventions and commercialization. The public receives access to new and useful improvements to machines, processes, chemicals, and more.
Why patent? In order to employ a powerful tool that – when used properly – helps inventors improve peoples’ lives and, ultimately brings glory to the Creator as they reflect His creativity and uncover and harness the wonders of His Creation.