Latinum is chosen as the default currency, exactly because it is not replicable. In ST:Outpost there’s an episode where they find an alien tech that is able to replicate latinum, but only for a couple days before it dissolves. That is than used by ferengi pirates for obvious malicious reasons. ST:outpost is a fan production though, so not canon, but I do believe this is how it is. It is briefly mentioned in the apendices on latinum’s memory alpha page