Helium makes up 25% of the atoms in the known universe, so one would guess that the inert gas would be quite plentiful on Earth
Unfortunately, a familiar property of helium prevents this from happening. Helium gas is lighter than air and literally rises into space, depleting the Earth of almost all valuable helium resources over time.
Source: http://www.visualcapitalist.com/helium-a-valuable-gas-not-to-be-taken-lightly/
