Tiny particles are still orders of magnitude larger than the particles you're fantasizing about.
And they serve a specific purpose.
The preon hypothesis was also very conjectural, not supported by empirical evidence, and somewhat unparsimonious.
Protons and neutrons belong to the hadron family, which is characterized by being made up of different numbers and kinds of quarks. Protons and neutrons are composed of three quarks each, but the electrical charge is governed by which kinds of quarks they are. The different kinds of quarks have different masses, and no one knows why. But that's why protons and neutrons don't have exactly the same mass (although they are very close).
Similarly leptons (the family of much less massive particles that includes electrons) come in different masses. Leptons are elementary particles, but no one knows why they have vastly different masses despite being the same in practically all other properties except charge.
Because the Standard Model attempts to bring order from apparent chaos, there is some interest in knowing why these particles have different masses when it seems they should be the same. Naturally the straightforward proposal is that they differ in mass because instead of being elementary, quarks and leptons are composed of even smaller particles—tentatively called preons—that account for the difference in mass. The preon conjecture says three preons make up all leptons and quarks but result in the different rest masses not by adding or subtracting preons but by placing the three preons in different energy states, like electrons in higher or lower orbits. Because energy and mass have an equivalence [nods in Einstein's direction], higher energy states give the preon higher rest mass.
Then you have to figure out what holds the preons together to make leptons and quarks. We know that the Strong Force (one of the fundamental forces in physics) holds quarks together to make hadrons, and holds individual hadrons together to make things like atomic nucleii and the Pokémon-like menagerie of short-lived hadrons. That means you need a new fundamental force, the Even Stronger Force. And you need a new kind of gluon to mediate that force—krazygluons, or whatever. And preons still need to exist in different variants to account for all the other properties besides mass that hadrons and leptons exhibit differently, like charge.
So a whole lot of speculative handwaving.
Certain parts of the preon conjecture are elegant, such as continuing the pattern of three smaller particles. But ultimately the E = m⋅c
2 equivalence doesn't solve the quantitative mass difference problem it was meant to address. The Heisenberg Uncertainty Principle says that the product of momentum and position can't be too small, because it's governed by Planck. So if you necessarily constrain a preon to a very tiny area of space—the volume of an electron—its mometum must equally necessarily be very high [nods in Hawking's direction] to compensate.
When I say very high, I mean relativistic speeds; almost the speed of light. That means their effective mass is extremely high—orders of magnitude more massive than we know an electron to be.
This is all math. The HUP is an equation. Computing the energy of relativistic velocity is an equation. Finding the equivalent mass of that energy is an equation. I've left out most of the equations for simplicity, but the actual solutions to them is what dooms preon theory to the scrap heap of physics.
The notion of "quadrillions" of smaller particles composing quarks and leptons doesn't solve any of those problems. It doesn't even address or contemplate any of them.