The purpose of unnecessary thought is to sustain the definition delusion.
The process of unnecessary thought is to mull over the model (reinforcing it as you say) despite there being no profitable outcome by doing so. Like the liver producing bile for an empty stomach
Unnecessary thought sustains the unnecessary, therefore avoiding the nothingness of reality.
Unnecessary thought, noise, chatter, the constant low-level buzz and drone of inner voices, ideas, images, detritus, flotsam and jetsam, one of the main functions this seems to have for me is to keep me amused, entertained, and to stave off the fear and discomfort bubbling away beneath.