Double-Income/No Kids.. coined early '60s IIRC.
All insouciantly--was this not? a much earlier dim-awareness of marriage being synonymous with: Official perks, from taxes to various sub-rights conferred:
re hospitals, bail! (can't be forced to testify!), deaths ... and similar Exceptions to general law codices. The religio-aspects were already quite secondary 'motives'.
Some were pissed that, DINKs could live high-on-the hog sans the joys of pediatricians, orthodontics, teen-age in-home savagery and the rest.

As to any redefinition of 'marriage': I grant you that the new basis, like the old is mostly about the financial, plus inextricably entwined with: the entire pseudo-'Science' of The Law:
all those 'rights', rites! and (legal-)Rights conferred as veritably altered folkways/mores--merely via the marriage agreement.

Unfortunately, because: Bigotry Is (not a rare mindset), your quite clear POV shall be submersed: when within company of the Reptile-brains extant
(not to be confused with the unusual sanity, tolerance and er, perspicuity of the IGM, natch.)

I need-not any disclaimers re bigotry; if your character is that fucked and I haven't noticed, well then I must be an incorrigible naif.
Simply, IME most folks have never?/rarely examined their own presumptions/analyzed "the roles of marriage in the US" beyond some casual curiosity.
Debating this issue amongst that large group would often trigger all those Freudian-'projections' from within their own unexamined/at least un-settled psyches--no?

[Which-all is why I never discuss such things] as: my proposal to replace the current crop of corporate-profitable Junk-food, super-market Shit-tomatoes etc. with..
a more honest, probably more nutritious --Newly Branded!--

Soylent Puce ... when You Care Enough to Eat the Very Beast



Carrion.. it's what's for dinner--but ya still gots to Pay for it.