Software engineering is a group effort with lots of components other than coding. It is very very seldom a lone operation and all those are tiny products with tiny scope (if results in a viable product at all!). Deciding upon the features, figuring out what is the best to do in a plethora of criteria involving finance, technology, organization takes much longer than the actual coding and involves the communication (spoken, written, presented, etc.), no suprise there.

Management could many times done better of course, managers are as lazy or incompetent as other people, if not more.