[atleta]

Indeed, depreciation (inflation) and (hopefully) being able to control it is an important feature of fiat money: this is what motivates people to invest it as opposed to just keep it under the mattress, i.e. out of the system.

Economists may be wrong, of course (a lot of times it seems that their math models are pretty crude), but no theory seems to support that keeping your wealth locked away is good for the society. (I deliberately didn't say economy, because optimizing for economic growth alone can indeed hurt the society if we don't channel all the important aspects in somehow. Think global warming.)