No one knows why. It will ruin his Special Day and he will always have parts left over. No one knows why. Good places to shop for men include Northwest Iron Works, Parr Lumber, Home Depot, John Deere, Valley RV Center, and Les Schwab Tire. It doesn't matter if he doesn't know what it is.
Men enjoy danger.
That's why they never cook - but they will barbecue. Tell him the gas line leaks. Everyone knows why. Men love chain saws. Never, ever, buy a man you love a chain saw.