American houses

I remember watching TV when I was young and noticing how American houses do not have any fence or gates around the house. You know how Malaysian houses all have big gates and wall surrounding the houses? I remember my dad bringing us to this new residential area, now famously known as Tropicana and I was totally amazed by how the houses there didn't have any fences surrounding them.

Aren't they afraid of people coming in?

Of course I didn't know anything about how tight the security is and all that. But the houses in America are like that too. No such thing as fences here. Stainless steel or pvc fence installation. You can go onto any person's compartment anytime. Though them being happy is another thing. I wonder which is better?