1. One spouse continuing to work provides the potential for higher Social Security checks (both because the still-working spouse can better afford to delay, and if it’s the higher-income spouse that continues, will also generate higher Social Security survivor benefits as well)
2. Working spouse may be able to access employer health insurance for the couple (often far cheaper than purchasing such coverage through a health insurance exchange for those who are not yet age 65 and eligible for Medicare),
3. Having ongoing income to either bolster retirement savings or at least reduce the need for retirement withdrawals (allowing the retirement assets to grow further and reducing sequence of return risk as well).
Wall Street Journal had an article discussing this topic in more details.