I think they don't want people to be district-shopping, applying here or there because they feel a particular location is faster or more lenient, resulting in some places getting flooded with applications based on whatever is popular with the word on the street.Question is, why there is a 3 months rule when you have been a Permanent Residnet in US and staying for last 5 years as a Green Card holder?
Jackolantern, people cannot choose the DO as they have to show residency in the state where they belong to.