Because value itself is arbitrary. It's not like time or physics. Value is not an inherent property of the universe.

Nothing has constant value

You're on to something: the 2% inflation target is just an arbitrary value.

It means your salary is constantly going down for doing the same work - you have to stay on the treadmill just to stay in place.

But if you're an asset holder then the prices of your holdings appreciate indefinitely, and governments get the power to levy this constant invisible tax on the workers.

Mark Blyth is an expert on the topic: https://youtu.be/GXBSNCysxiA

If money became worth more over time, there'd be an incentive to hoard it, which in turn would make it scarcer in circulation and worth more. Of course it's more complicated in real life, and the cycle would eventually break, but that's the gist of why deflation (what that is called) is seen as a bad thing.

Minor inflation is pretty harmless. Exactly 0 change in the value of money might be good too, but it's right next to deflation. So, the usual target amount is a percent or two of inflation per annum, to be safe. Central banks achieve this primarily by lending money out, at a higher or lower rate of interest as conditions demand.

banana for scale

Because this way you'll never know if it's just inflation or an ever growing markup.

Cause it allows you to have a Ponzi scheme in which you always assume the future will be more prosperous.

If money loses its value, that puts pressure on people with money to use it and try to turn it into more.

So unless your willing to lose money due to inflation, you HAVE TO get a return on your investment, thereby ensuring perpetual growth.

It works well when there is tons of room to grow, but then it all falls apart when you run out of that.

Once that happens, you just keep increasing the money supply, allowing capital holders to increase at a faster rate than workers. Even though workers “make more”, they have a smaller share of the pie.