If your fixed income (Social Security/pensions) doesn't cover your basic living expenses, an annuity can bridge that gap.
If market volatility keeps you up at night, an annuity acts as "personal insurance" against a market crash. Red Flags & Risks Should I buy an annuity or use drawdown? - The Times should i buy an annuity
If you expect to live well into your 90s, an annuity protects you from the risk of running out of money in your final years. should i buy an annuity