I know of some children who are in preschool right now and still wear diapers.
While, I agree that children shouldn't be pressured to use the toilet, I do think that getting them used to the idea of toilets early on is a good way to train them. Like the elimination communication seems t be a pretty healthy way of prepping children to want to use the toilet.

I work with kids and it's not good to introduce potty training before the child shows signs of being ready. But sometimes if potty training is introduced too late it can cause a lot of stress and embarrassment I think to a child when they are in kindergarten and all of their friends use to toilet and they still wear diapers.