The question then arises, if we almost never observe the higher generations of matter particles in our universe, why do they exist at all?
Without understanding why the second and third generation particles
exist, we cannot rule out the possibility that there are more quarks and leptons, with yet
larger masses. Possibly, the answer could be that quarks and leptons aren't fundamental, but are made up of yet more
elementary particles whose interactions manifest as the different generations of matter.