Why do some patents charge patent fees after 20 years?

1. In order to protect a patent by law, the State Patent Office needs to maintain the validity of its patent legal status, which needs to consume the relevant human and material resources of the State Patent Office, so the patentee needs to pay the corresponding fees.

2. Paying the annual fee is conducive to the effective use of resources. Through the annual patent fee, a patented technology that is idle in the hands of the patentee and cannot bring economic benefits to the patentee can enter the publicly known technology field as soon as possible, so that the public can freely use the technology and promote the scientific and technological progress of the whole society.