You forget Jim that the raindrops are falling! If you suspended one
(somehow) then sure - it would bulge at the bottom, but natural
raindrops are perfectly round.
In earlier times, ammunition makers used this to good effect to make
lead shot. They dropped molten lead from a height in a 'shot tower'
and by the time they solidified (before reaching the bottom) they
were nicely 'balled'.
FWIW