What is in doubt here, value provided by cash? A friend of mine uses (used?) cryptocurrency for transferring/receiving money to/from a sibling across the ocean

What is in doubt here, value provided by cash? A friend of mine uses (used?) cryptocurrency for transferring/receiving money to/from a sibling across the ocean. Converting to/from local currency is apparently cheaper relative to PayPal rates. (Plus, in some countries PayPal et al. restrict accounts not associated with a bank, making it even less attractive to unbanked.) What is unclear to me personally is whether benefits outweigh other implications, once everything gets amplified by scale.