The amount of currency does not have to correlate with the size of an economy. When the economy grows while the amount of currency stays the same then your money simply becomes worth more. For the overwhelming majority of history this was taken to be a good thing. The argument for inflation is that if money become worth more over time then it would discourage investment and encourage money hoarding.
That's probably not untrue, but that critique doesn't simply make the alternative better. Money becoming worth less, inflation, creates an arguably worse scenario where now wealthy individuals are motivated to hoard things instead of currency. For instance Bill Gates is currently the largest private landowner of farmland in the US. This issue is where you get the WEF also publishing their 'You will own nothing, and be happy.' goal. I find this more unpleasant, and even dystopic, than Scrooge nosediving into his stash of ever more valuable dollars.
Another major issue here is that lower classes are the most unable to deal with inflation. They can squirrel away some money, but in an inflationary system that's the last thing you want to do. For instance stuff like bank CDs are basically just exploiting economically illiterate individuals. Nobody wants money in an inflationary system, but lower classes need immediate access to their money for the next time e.g. their car breaks down, and they are extremely risk averse. The net result of this is a system that not only perpetuates but directly drives ever greater extremes of wealth inequality.