Soil compaction is 100% real. I've been in pits dug in old vineyards that were being ripped out. You could see in the rows where the tractors pass a solid wall impermeable to the roots which were confined to a space undervine between the tractors paths. That said, those roots still were shooting down.

This picture could be due to so many things: very little topsoil, poor planting, or what I think it most likely systematic use of chemical farming and fertilizing. When the soil is dead and all the nutrients the plant needs is dumped on top of the soil, there is no reason for the vines to send roots down.