The Wharton admissions committee wants the person who knows you the best at work – usually a direct supervisor – to attest to your skills, achievements, and qualities. They need that first-person POV brought to the table. Wharton wants to get the nuanced insight and real-world examples of how you perform with others.
Difficulty Deciphering Wharton's Letter of Recommendation Questions?
WHY YOU SHOULD NEVER WRITE YOUR OWN LOR’S
For one, it’s unethical. But even if you don’t care about that, you run the risk, of looking like a newb, as somebody who does not write a lot of recommendations. Secondly, you run the risk making your LOR's sound similar to each other. Thirdly, you run the risk of the LOR’s sounding very similar to your essays.