Chefs always add fat to everything -- I've seen them throw bacon into fat to saute. It's for flavor because fat makes stuff taste better to most people.
I was watching a CI show on spaghetti sauce and they soaked bread in milk, put it in the food processor and then added it to the beef before sauteing. I forget the chemical reason but evidently it eliminates that kind of rubbery texture sauteed ground beef gets in sauces.
Some days I pray for Silence, Some days I pray for Soul,
Some days I just pray to the God of Sex and Drums and Rock 'N' Roll.