Schemas seem to have been part of the SQL standard for a very long time, possibly from the first version in the 1980s. (I'm referring to Date and Darwen's excellent book, "A Guide to the SQL Standard".) So it is to the standards bodies, not the vendors, we should turn first if we think this feature is unnecessary at best and confusing at worst.

And I tend to agree it is unnecessary and confusing. All the vendor implementations are now very good at cross-database querying. (In the early years of RDBMS this was probably not so.) So in nearly every case where separate schemas might seem useful, separate databases would now seem to be a viable option.