The sidewalk boundry effect is well-studied and generally pretty well understood. You need that barrier just to have people walking around. What I'm suggesting is that the level of disturbance is higher if you are not in transit - in other words, that there's a difference in achievable comfort level desired for utilisation between "sidewalk people will use" and "front porch people will use."

Also, front porches were architecturally dead before home air conditioning became even remotely common, and the patio (or the back porch, if you prefer) serves just as well in terms of an exteriour (cooler) sitting space as the front porch did; I don't think the placement of that outside-space is relevant w.r.t. this particular function.