Over the years I have watched people willingly walk away from secular jobs to follow Christ's call. It is a difficult thing to walk away from a job. The person without much in this world is painfully aware of how close he is to depending on the welfare of others. If he has a family he is always mindful of the line between his children eating and not eating. Abject poverty, at times, seems only a step away, and most people will fight hard to not take that step.
A person with wealth, on the other hand, may struggle with potentially loosing it all... He may fight to keep what he has and dread the notion of having to trust someone other than himself to meet his daily needs.
The fishermen in this verse were the working class poor. They generally lived off a day’s catch. Yet… when Christ Jesus called them they immediately walked away from their jobs! They were, in practical terms, one day from not eating. It is very possible that Peter was already married at this time... wow... When Jesus calls how many of us will immediately forsake our nets and follow Him?