During the Revolutionary War we experienced hyperinflation. Why?
In the past century the year with the highest inflation was 1946. Why?
The decade of the 1970's had much higher inflation than the 1980's or the 1990's. Why?
You're absolutely right --why!
Maybe we'd be better off if we shifted gears and agreed on definitions-- especially in how were difining "wages", prices, and inflation. There're lots of good definitions out there-- how about we use the following from U Mich:
| Inflation | Increase in the overall price level of an economy, usually as measured by the CPI or by the implicit price deflator. | |
| Consumer price index | A price index for the goods purchased by consumers in an economy, usually based on only a small sample of what they consume. Commonly used to measure inflation. Contrasts with the implicit price deflator. | |
| Price index | A measure of the average prices of a group of goods relative to a base year. A typical price index for a vector of quantities q and prices pb, pg in the base and given years respectively would be I = 100Spgq / Spbq. | |
| Implicit price deflator | A broad measure of prices derived from separate estimates of real and nominal expenditures for GDP or a subcategory of GDP. Without qualification the term refers to the GDP deflator and is thus an index of prices for everything that a country produces, unlike the CPI, which is restricted to consumption and includes prices of imports | |
| Wage | The payment for the service of a unit of labor, per unit time. In trade theory, it is the only payment to labor, usually unskilled labor. In empirical work, wage data may exclude other compensation, which must be added to get the total cost of employment. |
If we use this framework, then we've decided that wages are the prices of one part of the economy --labor. If the price of labor goes up, this increase calculates out to a higher price average (sum of items divided by the number of items). If the average is up then the calculated price index number is greater, and that's inflation.
Then again, if these definitions aren't good with you feel free to offer something else.