Guy's have large items they keep. Motorcycles, Jeep, tools, guns, etc. It's all stuff that you keep.
Women keep buying expensive little trinkets that they give to the Salvation Army, Homeless Shelter etc. Candles, soap, towels you can't use, decorative stuff thats only in style until she sees it somewhere else. Seasonal crap, no need to expound on this. Every weight loss pill that comes on the market, and every vitamin that could be ingested. Much of this "stuff" isn't really what can be accumulated as some has a shelf life.
So guys have "stuff" but it's long term "stuff". Women have "stuff" in a smaller maintained volume, but it's more of a fluid volume and is maintained for a long period of time, so results in greater volume over time.