Bitcoin transactions are too expensive to be a viable legal tender.

Monero would be better imo and comes with additional privacy features. Satoshi expressed interested in baking in the kind of privacy features Monero has, specifically group signatures and key blinding, to name two (see: https://bitcointalk.org/index.php?topic=770.msg9074#msg9074). Nicolas Van Saberhagen (N.S.) is like Satoshi Nakamoto (S.N.). I believe there to be a connection. Maybe Satoshi went on to work with Saberhagen on Monero. I also believe Satoshi would also agree BTC is no longer the peer-to-peer currency minable on personal computers vision he envisioned and Monero is closer to that. Bitcoin is a great investment and store of wealth but as legal tender I think that ship has sailed a long time ago. I guess you could say Bitcoin Cash could be a better candidate for legal tender given the cheaper tx fees but that's a whole other argument.