Help me understand lobby

SFV is out, everyone and their mother keep blaming the lack of a good lobby mode. I never understand the importance of a lobby mode. SFIV allowed you to create a lobby and log into it but how is this better than just playing through regular matchmaking (you hit the button, you wait for a match and done). I remember losing some time watching other people playing while waiting for my turn and that was aweful. So can someone explain me what did I miss ? Is there some trick to make lobby better ?

If I lose in a lobby, sitting back to watch the winner play against someone else helps me learn and do better against that player next time.
Lobbies are important to learn, as more often, you’ll learn more from watching.