Sometimes, using nested content fragments just makes no sense to editors. Our case: making a cooking recipy. We'd like to break down the recipy into steps necessary to make a meal component (such as: mashed potatoes) including ingredients, and we have no need of reuse. If we'd split off the fragments into a seperate fragment, life for content editors becomes a lot more difficult - it's much easier for them to fill in everything inside of a single fragment view.
No multifield is available in content fragments
We have multifield available in content fragments, including the option to configure them in the model editor
Environment Details (AEM version/service pack, any other specifics if applicable):