A friend asked me why do you always have to saute onions and garlic before you cook with them? My answer was simple. Well...have you ever tried the same recipe WITHOUT sauteing them? Or...have you ever eaten a bit of raw onion verses eating a bit of sauted onion?
Onions are sharp and onioney before you saute them. When you saute them...it caramelizes them and "softens" the taste making them sweeter. Added to your dishes it's a MUCH different taste than if you'd added them without sauteing them. Pretty simple to me and much more of a preference kind of thing. Some folks like onioney mo' better-er.
In savory dishes...I don't.
On hotdogs...I do.