The electron is considered an elementary particle, like the muon. Yet the electron is far more stable. The electron can last for a very long time; old as the universe, even under drastic conditions. The Muon is more fly by night. Why the difference in longevity for these two elementary particles?
If we look at the macro world, if we break a rock down into its ions, these ions will outlast the rock. The substructure components can last longer than the macro object. On the other hand, when we deal with the substructure of matter, all elementary particles, except the electron, have a much shorter life, than even the starting matter, when removed from their larger scale confinement. Why is that? Only the electron is consistent with dividing the macro-world; smallest pieces last the longest.
One possible analogy, to the low longevity behavior of the substructure of matter; besides the electron, is the living state. Our body is made up of cells. Cells lasting longer as part of the body, then if we try to isolate then, unless we can provide the isolated cell, something similar to its home environment.
The cell is not the smallest unit of life, but it too can break down further into molecules. The DNA is sort of like the electron, both being elementary; to life and the cell, while also being very stable in or out of life. We can find pieces of dinosaur DNA. Both elementary entities are designed to last.
The electron is unique to nature; long lived elementary and autonomous. It has both mass and negative charge, yet is it one particle. How can one thing, have two things, and not break down any further, into those two things?
One way to answer this is that the electron mass and electron negative charge are a unified affect where mass and negative change can interconvert into each other, like cut from the same cloth.
The analogy is we have the north and south poles of a magnet. It appears to be two individual things; poles. However, we have never isolated a magnetic monopole, so neither pole can exist without the other. Both only exist as pairs. At some level, the electron as one entity unites mass and negative charge, that appears as the two poles of the electron, where each pole needs each other to exist. It sort of describe the unification of mass and negative charge. The positron is similar; positive charge and mass.
The importance of mass is that mass is the capacitance for space-time; General Relativity. The mass of the earth keeps our space-time reference stable. The expanding space-time of the universe does not overcome the space-time capacitance of the earth mass, for us humans. There is no evidence the pull of the earth†'s gravity has decreased over time due to universal space-time expanding.
The electrons and positrons may be throwbacks to when charge first separated from mass; led to charge attraction and annihilation heat, until the electron became the king of the hill. This created negative charge repulsion expansion, while adding an elementary particle, designed with longevity in mind.