A federal grant was offered to three universities to determine why the head of a penis is shaped the way it is:

MIT spent $100,000 and determined it's shape increased the probability of sperm reaching it's objective.

Berkley spent $200,000 finding that it provided increased stimulation which helps women achieve orgasm.

Alabama spent $300 and reported that the head of the penis is designed that way to keep your hand from sliding off the end.