Why can’t mosquitoes and flies be called unnecessary organisms on the planet?

People do not like mosquitoes and flies very much. Mosquitoes bite us and cause itching. They can also cause some dangerous diseases. Flies can also cause some illness and spoil food. But in nature they are very important, and accordingly they are useful for us. These insects serve as food for many animals. If they disappear, then many food chains will collapse. This will negatively affect the person. Also, due to the fact that they carry disease, it serves as a factor of natural selection that promotes evolution.