Social security income does not adjust for inflation, why?
Because perhaps you do not have it set to do so....
Click on Settings then Social Security... then enter a COLA in the second section and save. You should then see the Soc Sec blue on the graph rising over time instead of flat.
It is not tied to "Inflation" value that is on the Other Assumptions tab as the social security benefits are tied to a government issued COLA. Note that for 2010 and 2011 that value was 0%.