Works of encyclopedic scope aim to convey the important accumulated knowledge for their subject domain. Works vary in the breadth of material and the depth of discussion, depending on the target audience. [[encyclopedia]]
The "target audience" of Wikipedia is generally agreed to be everyone. Given this, the article on Kepler's laws is absolutely inappropriate as only a tiny fraction of everyone could even begin to understand the mathematics used.
It is, in fact, an example of a crap article.