Slaughter on the roads

In some parts of the world I have seen bridges over roads and highways so that animals can cross in safety. The cost of these bridges, which are built only for the animals, is seen as one of the costs of road building. Community groups make it clear that it is not acceptable to see their wildlife squashed all over the roads by cars.
In this country, the carnage goes unseen and without protest. In Manly, where there are a lot of green spaces, you can see blood and squashed bodies every morning on roads which adjoin parks. These native animals are not even removed from the roads by the culprits or witnesses, but just run over repeatedly until they are flat like a carpet.
Roads which separate two city parks offer no way for animals to cross without running the gauntlet of speeding traffic. Why are people so insensitive, that they allow such barbarism to continue without saying a word?