This is correct, but ambiguous. What, exactly, was the reason? The 90's client-server model involved fragile, proprietary stacks of non-portable client softwa

This is correct, but ambiguous. What, exactly, was the reason? The 90's client-server model involved fragile, proprietary stacks of non-portable client software and proprietary protocols. That model would have you "install" Google, Facebook and Amazon as separate applications. Ironically this has reappeared as "apps" on portable systems; it seems we've figured out how to make this work in constrained environments. I have been solving some internal admin problems with a "two-tier" framework; ng-admin + postgrest. The business logic lives in PostgreSQL stored procedures and triggers. Effectively the middle tier has merged with the database so a big moving part has been elided from the stack. One nice benefit is that the cost paid to implement business logic produces a database model, not an arbitrary accumulation of inscrutable middle tier `behavior.' The REST API simply reflects -- and is always in perfect alignment with -- the database model.