Cars are awful but there are other dangers to cats besides cars. There are dogs that frequently kill cats and other dangers like poisons. Cats are also responsible for several bird species going extinct. They should not be outside.
“A recent study by the Smithsonian Institution and the US Fish and Wildlife Service estimated that domestic cats kill about 2.4 billion birds and 12.3 billion small mammals each year in the lower forty-eight states. This is far higher—and probably more accurate–than previous figures, and likely exceeds all other sources of human-related losses of these animals. That makes it a major bird conservation concern.”
“Outdoor domestic cats are a recognized threat to global biodiversity. Cats have contributed to the extinction of 63 species of birds, mammals, and reptiles in the wild and continue to adversely impact a wide variety of other species, including those at risk of extinction, such as Piping Plover.”