It was uncommon for people to blend Daoist, Buddhist, and Confucian practices in a syncretic fashion. Why do you suppose this happened?

Even though these 3 practices have similarities, they also have very clear differences:

Daoism is different from Confucianism in a way that does not emphasize in practicing rigid rituals. Taoism does not focus in social order either like the way Confucianism does. In regards to Daoism and Buddhism, they have different views about individual life, society, and culture. They also have different views about reincarnation (life after death). Buddhism also believed that suffering was a critical component in life which could not be avoided. Whereas Daoism believes that life is all about goodness and pain is something that should be eradicated by attaining the right path in life.