Why consider non-farm payrolls? Why does the US consider non-farm payrolls when looking at employment levels? What are the reasons for not including farms? Are the workers too transitive, does it not contribute in a certain way to economy which is undesirable to measure? Other countries seem to have similar ways to measure employment levels which suggests farms payrolls are problematic.
Here is a link to a blog post aiming to answer your question. 

Also, I am not sure if you mean the NFP is problematic or if general payroll estimations are problematic. I would say the later is, and the blog post highlights some reasons why.