Also, engagement sessions are longer which gives us a great opportunity to get to know each other and for me to find your best looks. A photographer that just shows up to your wedding day having never photographed you (or even seen you before) may not get the photos that someone your experienced with will. I really think that having trust in your photographer to capture you from the best angles on your wedding day is vital to creating beautiful images.
To sum it up, proposals are a surprise. Engagements are planned.