Chests are one of the main loot sources found while exploring maps.
They are usually tied to points of interest, side areas, or hidden structures rather than the final boss encounter itself.
Current map pages show chests appearing inside points of interest. For example, the Forest Map page explicitly calls out:
This makes chests part of the reward for fully exploring a map rather than only rushing to the boss.
If the Virtual Loot Bag is enabled, gear looted during an explorable map is redirected into that bag instead of staying in your inventory immediately. The bag opens when you leave the map and clears between map runs.
This does not replace chests themselves, but it changes how map loot is reviewed after you collect it.