Of course there’s nothing that says wages should be indexed to inflation, however, inflation doesn’t just magically disappear if you don’t. That wage is being effectively depreciated, while prices do get adjusted, so largely it’s the employer that’s pocketing the difference. This happens not just at the lower wage range, but at any wage range. Low inflation is inherently not a terrible thing in economic terms (much more preferable than deflation or high inflation), but it does have that effect on wages and once enough time has gone on without some sort of adjustment, that’s how you get to non-livable wages.