Well, it is matter of exposure. From what you have seen, that's all they can do. In reality, there are all sorts of weights and styles of tarps. Here are some advantages of tarps.
Most tarps can be set up with at least slight variations, such as how high they are. That increases air flow and outside viewing.
Tarps weigh far less than any tent. A solo tarp, with built in netting, can come in under a pound.
Tents are often a nightmare to put in the rain. Throw up the inner body and let it get wet then the outter fly. With a tarp, you set up the "fly" and lay down your ground cover. Also, since they are usually so light, they dry very quickly and are much easier to pack away.
Tarps come in many styles. Yes, they can do almost anything a tent, including providing protection from multidirectional winds and insects.
What's all the excitement? Well, if you know about them, tarps provide more flexibility for a lot less weight.