As a pastor, I have the opportunity every week to share the gospel publicly in a way that most of the members sitting in our church do not. However, that doesn't absolve them of the responsibility for reaching others with the gospel.
I think we have to realize that God sometimes gives us more time to pray, and when he does this, we can pray that he will bless those who have opportunities to speak to others.
There are opportunities around. It takes time and motivation to take them.
I guess I tend to see divine appointments everywhere. I am always on the alert for opportunities. So I prefer to err on the side of witnessing too often than not enough.