What "things"? I have attended several public offices to do various procedures (e.g. Registro) and also used my green card in several private establishments (e.g. Europcar) and not had any problem.Moncloa still hasn't said that it's mandatory, therefore it isn't.
It certainly does seem to make things easier though.
Those denied boarding flights from UK without a TIE can tell you that!What "things"?