Firefox cleans infrequently

[hmt3design]

I primarily use Firefox as my browser, with Chrome as my secondary. I've gone to using CCleaner instead of just emptying the Trash. I've noticed that Firefox/Chrome only seems to clear files about once per week, and when it does clear them, it dumps about 3,000+. Shouldn't it be clearing the Firefox/Chrome cache every time I run CCleaner?

 

Also, I've noticed CCleaner clearing files from Internet Explorer. I don't use IE, and yet files show up every time as being cleared.

 

System Windows 10 Home, 64-bit, updated. (The same thing happened in Windows 8, so that wasn't it.)

Intel Core i7-4700MQ CPU @ 24GHz

16GB RAM

 

[hmt3design]

Found something interesting: CCleaner will clean the Firefox cache/session if Firefox is open when a "Run Cleaner" session is started. It has to close the browser (dialog box opens to tell you that).