Sheet Metal Flat Pattern Math

I have spent the past two weeks looking into the math of calculating bend deductions and k-factor and I just don't understand how to translate scattered equations from Steve Benson into a full method of determining bend deductions. 90% of everything I read tells me to just bend coupons and set up a bend table. My question is if everyone is using a test and check method to set up bend tables, what the point of the all the math?