The main reason that people purchase life insurance is to know that in the event of their passing, their children and loved ones will be taken care of. Life insurance can also help with the distribution of your estate. Your payout could go to family, charity, or wherever you choose to distribute it.
The main reasons to buy life insurance would be because you have dependents that would be put in a tough position without you providing for them. For example, if you have a spouse, a child, or a parent who is dependent on your income, you should have life insurance.
If you have a spouse and young children, you will need more insurance than someone with older children, because they will be dependents for a longer amount of time than older children. If you are in a position where you and your spouse both earn for the family, then you should both be insured in proportion to the incomes that you garner.
If you have a spouse and older children or no children, you will still want to have life insurance, but you won't need the same level of insurance as in the first example, just enough to ensure that your spouse will be provided for, to cover your burial expenses, and to settle the debts that you have accumulated.
If you don't have children or a spouse, you will only need enough insurance to make sure that your burial expenses are covered, unless you would like to have an insurance policy in order to help in the distribution of your estate.