Progression - the purpose

Last Month the Urban Sketchers blog from Portugal sent out a Challenge which was to show the progression of each drawing, usually in two steps: before and after adding color.

I actually usually do them in three steps:
1 - very rough drawing, almost only a sugestion, because they are made "on the go", without any support and in a hurry going somewhere (with a ink gel pen)
2 - in a table (with firm hand), finish and compose the drawing
3 - color (watercolor)

Here is an example of a building roof-top in NY:

 When the drawing is already "pretty" after step 1, I jump step 2. Here is an example in a Starbucks in Orlando.