Your family income situation might be different from other famil

1. In some income combinations filing separately saves tax legally.

https://turbotax.intuit.com/tax-tools/tax-tips/Family/When-Married-Filing-Separately-Will-Save-You-Taxes/INF22492.html

2. Filing separately shields the husband from the tax evasion of the wife. If the husband and wife decide to evade tax on the wife's business, both of them might agree to file separately so that the husband remains "innocent".