MotherGoose85 - To be honest my experience has been that a lot of friends who have waited until their children are 'ready' ie interested have found it so much easier to train them - often in less than a week.
I think you are being a little unfair to assume that parents are either too lazy, or expecting someone else to do it. As with so many aspects of parenting we parents are bombarded with different advice from all sorts of quarters including our own families, friends, books media etc and it is often difficult to pick out what is relevant to you, your child or your own family.
I have no doubt that there were disposable nappies 30 years ago but they were certainly a lot less common and considered a lot more expensive (I think my parents probably bought them for me for 'special' occasions ie things like holidays etc where they might not want. be able to do washing). However, I also have no doubt that disposable nappies nowadays do a MUCH better job of locking the dampness / uncomfortableness away from a child's bottom. And I also believe that this may make it a little harder for a child to 'get the hang of it'. However, as with so many things in life, thingsmove on and life has to adapt to deal with this.
It may be easy for you to say potty training is not rocket science but to a lot of parents (and I absolutely include myself in this) it is an absolute minefield. Books do not 'guide' you through the process as each child is so different I have found throughout my child's life that although books are useful, no author of a book knows my child like I do and no book is consistently right for me. If my son had read the books too then maybe it would be easier! However, I always find that there is some issue where we don't quite 'fit' into the books.
Have you considered that, generally speaking, 30 years ago most women had a bigger support network around them of friends and families with female relatives often at home. And in this way most parents themselves had been more involved in the upbringing of other relative's children so generally had more 'hands on' experience of children. I speak for many of my friends when I say that until I had my son, I had never held a child, changed a nappy or done anything at all to do with children. Thus it can be quite a steep learning curve.
I apologise if this seems like a bit of a rant, but I found the tone of your post a little patronising as someone who is currently trying to work out how to potty train my child in the way that will be easiest for him to get the hang of it.