First, some people do it regardless of whether others have patents or not, that is, they may not have patent awareness, or they are not afraid of knowing that they have patents. In fact, as the patentee at this time, they can sue him for infringement;
Second, although some patents have the same name, the improvement points (invention points) of each patent are different. Some people's products don't contain your patented invention, so there is the problem you said. Of course, some basic patents are different. As long as you make such products, you must go through patented technology, so some big factories with basic patents (effective) go everywhere to bid farewell to infringement compensation or authorize money. Maybe you still don't understand. Let me give you an example:
For example, Company A invented the water cup for the first time (hypothetically) and applied for an invention patent. Of course, the scope of protection of his patent is "a cup with a cylindrical body." If someone else makes any water cup within the validity period of this patent (the protection period of the invention is 20 years), they can't escape from his scope; Later, Company B applied for a patent, "The water cup has a cylindrical body with a handle on the outside." ; Company C applied for a patent, "A water cup has a cylindrical cup body and a cover for covering the opening of the cup body."
What I want to say now is that during the patent validity period of Company A, Company BC must get the consent of Company A before it can manufacture a water cup with a handle and a cover, otherwise it will be infringed. However, the patent of Company A has expired, and others can manufacture "water cups with only cups" at will, but they cannot manufacture the patented products of Company B or Company C at will.
In addition, it is good to know some characteristics of patents, that is, timeliness and regionality. Timeliness means that the protection period of a patent is limited, 20 years for invention, 10 years for utility model and design. Regionality means that you can only apply for China's patent in China, but not in the United States. If you add a good product, you can apply for a patent in the United States instead of China, then you can implement it in China for free.