Lots of apps are like this and I don't understand why. They should be using the caches folder and "the system may delete the Caches/ directory to free up disk s

Lots of apps are like this and I don't understand why. They should be using the caches folder and "the system may delete the Caches/ directory to free up disk space". However I have never seen this happen. When my phone runs out of space I have to manually delete these apps. Are they not using the correct folder, or is the system not deleting the caches?