The issue is not so much "fixed" income, but "lower" income. even if you have a DB pension, and max CP and some OAS you are probably at a district reduction in annual income from when you were working. If you've saved well, paid your mortgage and other debts you are probably well off, but still at a fraction of your working income. If you don't have those things you have even less income. 

Unless the math has changed, a percentage increase of a smaller amount is less than a percent of a bigger amount.