Although we are all human beings, each one has a different mind, different defilements and so forth. In order to suit every level of our minds the Buddha bestowed an enormous amount of teachings.
One kind of teaching is not enough. Just as we require many medicines in order to cure the different types of disease, similarly in order to help the limitless sentient beings, the Buddha also gave many many teachings.
'THE NECESSITY OF MEDITATING IN THE CITY'
by His Holiness Sakya Trizin.