But WHY Must I Help With My Own Application?

An application can be denied even before an interview.

Recently I Answered the Following:

"Me an my spouse (F-1 student) are in the process of concurrent filing. We were wondering if it is really necessary to include hard evidence such as: joint bank statements, auto/health insurance, car titles, bills, rent lease, photos...etc with our application package, or leave until we are called in for the interview?"

Short, Sarcastic Answer: 

Sigh.

A Little More Helpful Answer: 

It depends on a noncitizen's tolerance for risk. An adjustment interview is not like a consular interview where one necessarily brings supporting docs to an interview. Without adequate supporting documentation of a bona fide marital relationship, an application may be denied before an interview is even granted.

Having said this, the items listed are common documents to demonstrate a bona fide marital relationship. A marriage certificate is not enough. In fact, joint financial statements are specifically listed in the I-130 instructions, so I would categorize those documents as necessary.  My own recommendation to clients is that, since you've come this far, why would you risk a denial simply for lack of an little extra effort to ensure approval. But not everyone feels that way.