My friend does leather carving and he also uses a lot of flowers in his work and I asked him why. He said that most people start out learning to do flowers because most of basics are taught through flower work. He said it's something that even beginners can do nicely but also allows for the use of advanced techniques and personal expression.
I must say, watching a leather craftsman in action and seeing the designs slowly emerge from a smooth piece of leather is mesmerizing.