There is likely just a couple of folders inside the Cache folder that is consuming the most amount of storage. I am sure you have opened the Cache folder and sorted by size to see what they are. Developers can also add to the Cache folder and you won't see those cleared automatically, unless you run into a storage constraint. Feel free to erase any folder from an app that you no longer use and be selective about anything else you choose to delete. Constantly clearing your cache folder is just going to slow your computer down.
I am sitting at 6 gig and there is no need to remove anything, 17 gigs may be a bit excessive, but may also be used to prevent network access that will delay data loading. There is a trade off there. Clearing the cache has been a long time fallacy of Cleaner/Optimizer programs that claim it as a benefit, and it really is not.