If the tax penalty is smaller than the savings from sharing a household, it's still an advantage to be married vs single and living alone.
Spread the word!
https://apeopleschoice.com/common-law-marriage-in-california...
You can also file married income taxes if you are legally married in your state of residence. In fact, if you didn't it probably would be considered tax fraud.
Family health insurance plans
Unlimited tax free inheritance
Spousal social security and pension
Social security survivors benefits