We’ve turned airports into shopping malls, because airline passengers aren’t an airport customer they’re the product to be sold to. Longer dwell times to fill with shopping, therefore, have become a feature not a bug.
Restaurants, too!
Even if you resist the urge to buy books and souvenirs at the airport, arriving 3 hours early will probably mean you need to eat a meal that you would have otherwise eaten at home or at a cheaper restaurant.
And even if you're not hungry, you might choose to sit in a comfy seat at one of the airport bars, having a few drinks and appetizers.