As women encounter new sexual partners some have bigger dicks than the last biggest size dick they encountered then it take more to 'fill them up'.
Example...
Say a woman's first is 5 inches long then her 2'nd is 8 inches long & she slept with him for 3 months & then she sleep with her first again... well he can't do the job any more length wise.
It's simple math imho
Maybe im wrong