The prime reason for selecting a tarp over a tent is weight savings, which can be significant over the course of a multi day trip. They are not particularly difficult to pitch and can offer surprisingly good protection.

A worthwhile compromise is selection of a tent that can be pitched with just the fly, poles, and ground cloth - more protection than a tarp and easier to erect, but lighter than the full tent. In bug season, just carry the tent - you will be glad you did.