The penis produces fluids in order to keep itself moist, to alkalize the vas deferns and the urethra (to ensure the survival of sperm), and to lubricate whoever you're having sex with. When the foreskin is cut off, these unfortunately leak all over your underpants and create a mess, while leaving the glans completely dry, The foreskin holds these in, and that's why you have to make sure to wash it every day; the killed-off bacteria can have a very "penisy" odor.