I agree that cats should probably be inside for environmental reasons, but I don't care if cats live somewhat shorter lives if they are outside, because they are obviously very happy when they can go outside.

Our cat is pretty depressed during the winter months because she can't go outside (well, she can if she wants but she rarely is because it's very cold and often snowy), so she just goes around meowing at shit because she is bored. During summer she is outside a lot and is noticeably happier.

The same applies to humans.

And it's not like we live next to a highway like seemingly all Americans are, we have lots of outside cats in the neighborhood and they have been doing absolutely fine for many many years.