When you are in a job it is easy to not consider what would happen if your work situation changes. It may be that you start a family and one of you has to leave work, or it may be that you are due to retire soon. For some people, their situation changes with very little warning such as if they get made redundant or have to leave work due to personal circumstances. This can put a lot of financial strain on a family or individual.
Ideally when you are in a job you should be trying to put away a little every month for a rainy day. This may be by paying in to a savings account and or a pension. This can be easier said than done as often people have very little money left at the end of the month to save. Many employers now often work based pensions where they will also pay a certain amount in to a pension for you. The amount you pay in is taken out of your wage prior to tax and therefore will actually save you money in the long run.