Many businesses exclusively accept WeChat and Alipay. So there is a mechanism for paying rent, utilities and tax. Otherwise they would run out of cash.

To replicate that level of success, Facebook must create a mechanism to convert tokens back to cash.

So the tokens are basically just used to get past regulations. Facebook will then gather some hard numbers to show that crime is negligible. Sensible governments will tolerate the tokens because it's replacing physical cash where crimes like tax evasion are rampant.