What state subsidizes? The Earned Child Tax Credit only applies when you have children, not for being married. The benefit of filing married jointly is to potentially get into a lower tax bracket. Your incomes become one and are taxed on a different scale than single filers. Its not a huge difference but it could mean the difference between owing taxes and not. It's meant as a way to limit paperwork from the IRS, not promote family cohesion.
There's no effective difference between a subsidy and a tax cut. To cut someone's taxes is to subsidize their behavior. To reward people for adding no extra value to society is untenable to the future of that society. A state interested in maintaining the well being of its people should only subsidize behavior that leads to the continuation of the state and society at large. It's why I don't support national healthcare unless we ban unhealthy behaviors, such as obesity, drugs, and homosexuality. If you make it the state's business to pay for your healthcare, then you make it the state's business to punish you for choosing unhealthy lifestyles. You can't have one without the other or the healthcare system is doomed to failure. The lack of this kind of long term thinking is what is causing the slow degradation of Western nations. It's why Western nations have such amazing healthcare systems and yet such unhealthy populations.
First off, I'm still waiting for the tax credit on being married. What's it called? If you want to call "married being in a differnet tax scale" then sure but it's really not.
https://smartasset.com/taxes/taxes-single-vs-marriedIf you notice, having two people with the same income doesn't really help. Their effective tax rate is going to be about the same.
Ex:
I make $40,000 a year.
My wife amkes $40,000 a year.
Separately we pay...
10% up to $9,525
12% from $9,526 to $38,700
22% from $38,701 to $40,000
Which totals....
952.5 + 3500.88 + 285.78 = $4,739.16 (x2) = $9,478.32
Jointly we'd have..
10% up to $19,050
12% from $19,051 to $77,400
22% from $77,401 to $80,000
1905 + 7001.88 + 571,78 = $9,478.66
Huh... look at that... it's actually 34 cents MORE if you file married. Not much of a tax credit is it?
This, of course, is before tax deductions. But the deductions are just double the single ones so... Yeah.