It's not that you're "poor" if you make less than $30k, it doesn't depend on whether you're supporting family, it's that it's not possible to legally exist as a single person household working full-time at $15/hr; You are either receiving charity or you're securing your person through some sort of criminal act (squatting, living in your car, living in a park, sleeping in the breakroom at work, living in an illegal basement apartment or having five roommates in an illegal sublet), or you're delving into the 60-80 hour workweek.
Provisions which trigger at the federal poverty line for a single person not receiving private charity, require that you have been involved in criminalized living arrangements for a long time, and also that you have some sort of fixed address by which to reach you.
Why is that the goal? When I was in my late teens / early 20s back in the 90s making low 30s, I did what everyone else my age did: got a roommate.
It's not great most of the time.
It was, however, very motivating for me to improve myself so that I could afford to get my own place.
Several issues that real people today are suffering with is that it's hard to remain a 2-income family and have young kids. Someone's got to take care of them, and daycare costs more than the median worker is likely to make in the limited time your kids can realistically be in daycare. So now you're down to 1 income, expensive rent, or 2 incomes, expensive rent and expensive childcare. Or 2 incomes and live with someone's parents who may also watch the kids, which while some cultures are fine with that, others resent that being their only option (especially if you can't stand those parents!) -- and for elder millennials and older, we generally were able to have better options if we planned our careers wisely. I cannot imagine any advice I would have given to two 18-year-olds from poor families in 2020 that would have set them up to be on track to have kids and live independently anytime. Especially if they were determined to go to college, which everyone is told they must do.
But CPI figures aren't what we have to deal with.
Average rent in 1994 was roughly $500 ($6000/year). Today it's $1400 ($16800/year).
You were paying (if a median unit) 15-20% of your income in rent and felt that this was too much and you needed a roommate.
Today there are lots of people making $32000 a year at full-time jobs (that's $16/hr, pretax), or LESS than that, and being told that they need to pay more than 50%. Or that because they make so little (we credit check tenants now!), they simply are not allowed to rent legally.