As I am sure all readers know the true passive is available in Spanish but is commonly avoided. By true passive I mean the one formed with the past participle. For instance this question and answer to When should I use the pure passive voice in Spanish? ( fue/fueron [past participle] ) suggests that Spanish prefers the voz pasiva refleja. My fairly ancient grammar devotes about one page to the passive and two to how to avoid it and it only gets on to that in chapter XXIII out of XXV.
This has often puzzled me and I wonder whether this has always been the case or whether this is a modern trend. I appreciate that historical answers can only consider the written language and it is my impression that the passive is even less common in the spoken language.
Note I am now really confused about this as the people who commented state that my assumption is incorrect but in his recent reply to this question @Rodrigo clearly states that what I defined as the passive is indeed avoided in Spanish in favour of what he calls the reflexive passive.
Note 2 I found the initial comments very instructive and helpful in clarifying my thoughts and teaching me some more about Spanish terms for Spanish grammar. They also made me realise that things which I put in my original question which I had hoped would provide background in fact served to obscure things. For instance if I was starting from scratch I would not have used the reference to the grammar book. For me the fact that it devotes so few pages to the passive and that so late in the book reinforces the view that it is not that important or widely used either in English or in Spanish whereas some people drew the opposite inference from it. In retrospect I would not have used the term 'avoid' either which was clearly wrong and unhelpful. I think in the light of the comments I would have asked something like: Did the form of the passive with se always co-exist with the form with ser + past participle or is it a recent development?