What currency do you propose people, companies, and countries trade in? And why that currency?
A currency is abstraction for trade in wider circles where (the common case) trade between two parties isn't sufficient ( typically parties supply | demand a basket of various resources, various energies, various intermediate and finished goods ) and for trade to take place the guarantors must have faith in the agreed abstraction for transfer of credit; additional mechanism that verify transactions are an added bonus.
Both now and through history many currencies have been used and are being used.
I've given examples of US dollars, the Pound Sterling, in the context of this sub thread bitcoin is an obvious example of a currency that has been used to facilitate trade; less obvious but important examples of currency are the word of a trusted person of faith (as used historically along the original Silk Road and today throughout Hawala and similar mechnaisms).
What strikes me as odd about your question is the implicit assumption that I favour one singular currency over all others.
In abstract terms, independant trade without ties to a dominant financial gorilla (once a time the pound sterling and perhaps one day the Yen (or other)).
That was a clean enough goal from the outset, my personal objections (expressed in cypher forums back in the day circa the bitcoin paper dropping) are wrapped in the failure to tie the OG bitcoin to some form of verified "energy used to mine" signature (a curly one) and the high energy cost of verifying OG bitcoin transactions.
With 20/20 hindsight it was likely a premature release, in fairness it was more of a proof of concept begining that lasted longer than expected and then took off.