What you're talking about is inflation of the currency, and if you want people to continue using it as a currency you'll limit its inflation. And taxes exist f

What you're talking about is inflation of the currency, and if you want people to continue using it as a currency you'll limit its inflation. And taxes exist for a plethora of reasons, originally as a source of income for governments, and later as a social and economic tool of governments to control behavior and growth, amongst likely hundreds of other reasons.