> its the right of inheriting when your spouse dies
You can designate your own heir.
> its the right to be covered by your spouse's insurance
> its the right to share joint custody of children
> its the right of spousal privilege in court
> its that you can file taxes jointly
> its the rights to benefits as a spouse of a veteran
> and dozens more of trivial and important legal rights most couples take for granted
And I am arguing that these are not things that should come with marriage - people who decide to not get married and people who are not legally allowed to get married (such as people in polyamorous relationships) should have the ability to enjoy the same rights as married people. Regardless though, not all of these are part of the universal definition of marriage (nor are a necessary part of it), the UDHR says that marriage as an abstract concept is a human right (and only for certain people at certain times as the law allows) - it does not designate any specific privilege between married people as a human right.
> If the government would stop meddling in all the other legal affairs ...
There is a difference between the government attempting to catch someone who violated the rights of someone else and the government recognizing (or not) the love between people.
its the right of inheriting when your spouse dies
its the right to be covered by your spouse's insurance
its the right to share joint custody of children
its the right of spousal privilege in court
its that you can file taxes jointly
its the rights to benefits as a spouse of a veteran
and dozens more of trivial and important legal rights most couples take for granted. These are trivially denied in many social interactions and used to make others feel like second class citizens, and deny them their pursuit of happiness. This was all debated and settled by the Supreme Court in 2015.
If the government would stop meddling in all the other legal affairs then I would see the reason for your confusion why they are meddling in marriage.