Trapping animals is allowed in many places for a variety of reasons. One of the main reasons is to manage populations of certain species that may be causing damage to crops, property, or other wildlife. For example, trapping may be used to control populations of beavers, which can cause damage to forests and agricultural lands, or coyotes, which may prey on livestock.
Trapping is also sometimes used as a method of wildlife management for certain species that are overpopulated or have become a nuisance. In some cases, trapping can be a more humane way to capture and relocate these animals than other methods.
Additionally, trapping is sometimes done for commercial purposes, such as to harvest fur, which has been a traditional source of income for some people.
It's worth noting, however, that trapping is often heavily regulated, with laws in place to ensure that traps are used in a humane manner and that certain species are not over-harvested. There are also many organizations and individuals who advocate for more humane and sustainable approaches to wildlife management and who work to protect animals from unnecessary suffering.