The balance stays the same, but buys less
When prices rise, the same amount buys fewer goods and services. A future account balance alone does not tell you the standard of living it can support. Consider the purchasing power of retirement assets or a maturity payment alongside its nominal amount.
If inflation stays at 3% for 20 years, a future $100,000 has purchasing power equivalent to $55,368 today. This measures what the balance can buy, rather than a loss from the account.