Hi strandsofpearl,
Welcome to the Mattress Forum! 
First, realize that this choice of what to use as the appropriate support structure under any mattress is always at the discretion of the manufacturer, and you’ll always want to follow this guidance for warranty reasons.
There is more about the different types of foundations and why they are used/recommended at the beginning of the foundation thread here. Specifically, from post #3 linked to in that thread:
In most cases … at least in North America … the layers in a foam mattress are designed to be “stand alone” in terms of how they feel and perform and the foam is designed to do all the work and only needs a firm and evenly supportive surface underneath it. In Europe … thinner mattresses are more common and the bases underneath them are often designed as an integral part of the overall performance of the sleeping system and it’s much more common to see more flexible foundations (often with flexible slats) under a thinner mattress. Even in North America though … you will find some manufacturers that design their mattresses to be used over a flexible boxspring which is an active and important part of the complete sleeping system (although again this is usually with thinner mattresses). There are also cultural differences between mattresses in different areas of the world which leads to some designs being more “familiar” (meaning they would sell more easily) than others.
“Back in the day” most latex mattresses were thinner and firmer and an actual coil box spring was used to make a difference in comfort, and in some cases was simply a “holdover” from what was being used with innerspring mattresses. These days, most latex mattresses are designed so that an active box spring unit is unnecessary.
Phoenix