There are a few reasons for picking Mercator, but the best reason is that north and south are straight up and down, and east and west are straight left and right — on some of the other projections these lines would curve or deviate as you move across the map.
Prototyping a Smoother Map
Antin Harasymiv

Google Map 直至最近仍然採用麥卡托投影,這樣雖然會令高緯度地區的面積受到很大的變形,但別忘了──Google Map 的用途是導航地圖,而麥卡托投影的用途也是一樣──協助船舶導航(地圖上不同緯度之間的兩點的距離顯示為一直線)。