The reason most sailboats go bow in to a slip is that they turn better going forward. It is easier to go bow in. When you leave the slip, there is generally more room coming out of a slip to turn. It isn't that much of a difference though. More like parking a car. Front first is just a bit easier.
1986 Sea Ray 390 EC
Garmin 4212 Chartplotter
Garmin 24 HD Radar
Garmin 546s Plotter
Engines
454 Crusaders
Are you surprised to see a sailboat backed in? There are several sailboats at my yacht club that back in. Some are over 40ft. Not difficult for an experienced captain.