Curious why admin forms do not render form_rest?

I’ve noticed that forms in AdminBundle do not render form_rest (by using ‘render_rest’: false).

I was wondering why was that?
As far as I can see, it would make extending types slightly easier and shorted by 1 step as making custom templates would not always be necessary.

So am considering overwriting the CRUD Create / Update _content templates to render the ‘rest’, any potential issues I should be aware of?