There's a point in our lives when we realize that we have to make a choice about God.
Elisha was called by Elijah, Elijah perhaps foreshadowing Jesus' call.
It isn't that we shouldn't bury our dead, or that we shouldn't take the time to say goodbye to people. It's that it is so dangerous and so tempting to look back. Then we are also tempted to say "Tomorrow, tomorrow I will follow you". Tomorrow comes, and it becomes today, and the present is always so full of things to do, things to bury, things to say goodbye to. It's like saying "Lord, I want to follow you, but before I decide to quit my bad drinking habits, I need to get drunk just one last time".
We shouldn't look back when we say yes to Christ, but it's never that easy.