The question of shotgun weddings was asked in its most general sense. I don't think anyone said or is saying that in any and all circumstances getting married is better than the alternative. Yes, in a particular situation the wedding might not be best. But a particular set of *special* facts has to be considered separately from the general principle.
With respect to privilege, the question of whether making it is harder or easier for some people doesn't change what is required to make it. If there's a woman who has to take care of her sick mother, had an alcoholic father, grew up destitue, has to work full time while finishing community college, etc, she has it way harder than the kid from the suburbs who has his parents paying for him to party at the frat house every friday. But the thing is that the relative difficulty of either situation doesn't change what is required for both to succeed: pass your classes and get the degree.
Working "hard enough" or "harder" isn't what is necessary, it's doing whatever is necessary to meet the standard.
It's similar with building a strong community. The principles are the same. We need strong and stable families. Marriage is the principle component of that, and the way that's done in the inner city is the same way it's done in the suburbs. Yes, some people have certain principles because of their upbringings, but that's likely because living by those principles was part and parcel of what shaped that family. And while you may not have said it, bringing up privilege here seems (to me) to be the same logic that leads people to say that marriage is for white people. Even if there's an oow pregnancy where the parents shouldn't wed, I don't see what that has to do with one's socioeconomic class. Like, "She's from the projects, so it's unreasonable to expect her to get married." What would that have to do with anything?