Winning is important but winning is not limited to winning only games. Winning can broken down into components of the game whether it be winning by quarter, winning by competing, winning as measured by defensive stats, TO goals, field goals attempted etc. Emphasizing winning the game only leads to all kinds of decisions detrimental to child development. Handling losses is a life lesson that will often be needed when these children grow into adults.
I'm not saying winning should be the primary goal of every game but winning does help get buy-in and enthusiasm from the players and parents. Everyone is a lot more excited about practices and games when you are 9-1 as opposed to 1-9. I think you should have competitive practices and competitive drills. We try to have a winner or record to beat in almost all of our basketball drills. It keeps the boys focused and motivated just like it should be in a game. An example from yesterdays baseball practice...the boys pair up to warm up their arms. You see lazy throws and just a lack of focus (they are just warming up). We then have a contests for which pair can make the most throws in 30 seconds without dropping the ball and you see more focus on their throws and catches and the competitive spirit comes out to want to win. I used to think a player was either competitive or not but I now see boys that I did not think were competitive have learned to be competitive because it is what our practices are all about. That competitiveness and will to win gives them more focus to practice better which ultimately makes them and the team better.
Goals should be to build life skills, to develop, to help realize potential...winning may (or may not) be a consequence of that. But there are too many external factors that affect a result, meaning winning should never be the focus. If you do, it is a distraction from the task in hand.
Redefine success in youth sports, not based on results or trophies, but based on how the athlete/team grow over the course of their time together with the coach