Apparently arch bridges are durable, cheap and simple structurally and a deliberate choice of many different types of load bearing structures. I never thought much about an arch in a bridge until today. Never would think that it mattered much and was more design/fashion rather than trade off against the forces of the earth.
Curiosity only arose because I wondered why x bridge has an arch which looks complex compared to a flat bridge? Just want to get over to the other side.