Also, with a lot of banks, the object ball travels a shorter distance to it's destination. With a kick the cueball sometimes has a longer disnace to travel to kick that object ball.
Also, since you are not hitting the rail first on a bank, your bank shot is more accurate since your hitting the object ball directly. Most of the time you know how the balls roll, sometimes you come across rails that act much different.
Plus like fred said. You can play with left, right top, bottom english and still make initial contact with the objet ball nad have a good chance of hitting the bank. With the kick, your english as to be on spot or else the cueball will take a totally different path off the rail.