It's easy to find negative things to say about spectators (the word itself even used as a negative description at times) because there are so many things where you could say that more people should be helping out with the work required in the world.
However there is a positive side to spectating the achievements of others.
C. S. Lewis once wrote in my favourite book 'The Screwtape Letters' that God wants human to able to celebrate their own achievements as much (but no more than) as if the same thing had been achieved by somebody else. If an architect looks at an impressively constructed monument, he should celebrate it's beauty the same regardless or whether it was designed by himself or a different architect.
Lewis wrote this as an explanation for how God wants our hearts to move away from pride, but his imagary also highlights for me the benefit of spectating. When you watch sports, you are practising the simple yet important action of celebrating others achievements. The more practised we become at that, the easier it should be for us to balance our humility in the way God intends.
There's nothing wrong with joy in your own success, and spectating is healthy because it keeps you well practised at taking joy in the success of others.
