Why do web designers make it difficult to see the actual photo? They've gone into the trouble of putting an enlarge icon (and needed code), but it still display

Why do web designers make it difficult to see the actual photo? They've gone into the trouble of putting an enlarge icon (and needed code), but it still displays a small window. I can understand that it's there to deter simple users from getting access (especially since the posters are for sale), but if they don't want to show the full resolution file then don't put it online and use a low-res one :-) https://store.pacificwarmuseum.org/uploads/products/navyaircraft.jpg https://store.pacificwarmuseum.org/uploads/products/navyairc... https://store.pacificwarmuseum.org/uploads/products/ArmyAircraft_002.jpg https://store.pacificwarmuseum.org/uploads/products/ArmyAirc... https://store.pacificwarmuseum.org/uploads/products/japaneseaircraft.jpg https://store.pacificwarmuseum.org/uploads/products/japanese...