CPI is an aggregate measure which munges a bunch of things together under a single statistic.
In fact, the cost of necessities has overall risen faster than the cost of discretionary goods. This has been generally true since the mid-1990s; prior to that, inflation differences were much smaller across income groups despite lower income groups spending more of their income on necessities. In some periods like the post-COVID housing and energy price shocks, the differential effect of real inflation on basic necessities has been even greater.
Even "small" effects compound over time. For example, when someone in a low bracket loses 10% purchasing power after many years, the net economic stress they experience is much greater than for someone at a high bracket. Differential inflation of necessities vs discretionary goods magnifies this.
In fact, the cost of necessities has overall risen faster than the cost of discretionary goods. This has been generally true since the mid-1990s; prior to that, inflation differences were much smaller across income groups despite lower income groups spending more of their income on necessities. In some periods like the post-COVID housing and energy price shocks, the differential effect of real inflation on basic necessities has been even greater.
Even "small" effects compound over time. For example, when someone in a low bracket loses 10% purchasing power after many years, the net economic stress they experience is much greater than for someone at a high bracket. Differential inflation of necessities vs discretionary goods magnifies this.