Worst-case scenario, in the dystopia we seem to be heading towards, employers or governments could control what the employees/peasants are permitted to spend their money on. I could imagine something like:

"At least 50% must be spent in your local district of your '15 minute city'. Purchases of alcohol, meat, and fossil fuels are prohibited. Unspent currency expires after 30 days and cannot be rolled over to the next month."

"Only senior management and above get paid in 'unrestricted' currency."