The US "poverty line" is at 80th percentile of world incomes. The US's vast welfare/entitlement system ensures few indeed net less than that line, shoring up their shortfall with trillions of $.
What constitutes "poor" keeps shifting. There will always be a bottom 10%. There is ongoing increase to the standard of living, instilling a sense of "nobody should go without X" (when X didn't exist not long before, broadband internet being the latest). Affordable housing gets overrun by population growth & attracting mobile opportunity-seekers, living space naturally going to the highest bidder; property taxes being a thing, there is no recognized natural right to real estate. Health care relentlessly advances, new lifesaving care objectively costing a great deal ... vs a public sentiment of a right thereto.
We need an objective redefinition of "poor", predicated on a baseline of nutrition, housing floorspace, basic tools (stove, disposal, etc), care (minimum optimistic odds of longevity), information access, etc and an understanding that the baseline cannot be shifted - that those doing better are not poor, that accessibility thereto is largely attainable (whatever the sociopolitical system), and acknowledgement that when/if all are above that line, poverty services are officially out of a job.
As it stands, "poor" is a moving target for which a great number of people have a vested interest in covering a consistent, if not growing, population.