As jno says, it had to start somewhere.
The Germans had been in France since 1940 and Hitler had been expecting an attack for a long time (and the allies had been planning an attack for a long time).
Hitler decided to build his Atlantic wall all along the Northern coast of France, and even through Holland, Belgium etc.
He chose Rommel to be in charge of building this "wall" and they spent a huge amount of money laying mines, laying barbed wire, building tank traps, building concrete gun emplacments and so on.
Anywhere the allies landed they would have met huge resistance and there would have been much loss of life.
The decision of where to land was given much debate, with some favouring the shorter crossing to Calias, but it was even better fortified than Normandy.
But even after they had taken the beaches at Normandy it took them months to fight there way inland, through the bocage, the dense hedgerow country of Normandy.
After the slaughter on the beaches many more men were killed fighting there way out of Normandy.