You can use it for either predictive or explanatory purposes. In the early ('00s) years of Google it was common to diagram out the incentives of all the market participants; this led to such innovations like the use of the second-price VCG auction [1] for ad sales that now make over a third of a trillion dollars per year.

[1] https://en.wikipedia.org/wiki/Vickrey%E2%80%93Clarke%E2%80%9...