Alright, we know that there is a seemingly infinite amount of universes. But remember when Rick said that they can only ditch their own universe (and replace another Rick and Morty) for maybe 5 or 6 times in Rick Potion #9? And why did the voucher for one free Morty mean anything if there are so many universes? Especially since that think was given as an apology for nearly sending a Rick to a faith worst than death.
So, I had that theory on my mind for about 6 years but never wrote it down. Well I did it here about 1 day ago. Anyway, let's look at the problem.
First proposal, the multiverse is not truly infinite but just really, really, really big. Why? Basically every time a decision can be made the universe splits and takes both decisions. Every particle that may move in two directions will split the universe into two copies. This means that the universe constantly splits into new realities. A mindbogglingly big number. But not infinite. Just nearly not infinite.
So, like the universe has a (gigantic) size, the multiverse has also a (gigantic) count of universes.
Still, this should still mean that we have a quasi-infinite amount of Ricks and Morties, right?
Well, we can omit all universes that are barren. This not only means no live, this also means every universe that never created a Rick or Morty. No Rick and Morty means no live to replace and no Morty for a Rick that is missing one.
But this is still an incredible big number! Well, only if not something equally infinite balance out the math. A very big number divided by a equally big number results in 1 after all.
So what could be something that is (a) universal to all universes that can harbor a Rick (b) so incredibly deadly that it rivals the size of the multiverse?
The answer: Mortys incompetence! The incompetence of session 1 Morty, to be exact. The Morty that hasn't yet learned to handle Rick. The only force in the universe that can counter the incredible size and weight of said universe.
Remember that Neutrino Bomb from the Pilot? The very first scene we saw? Tell me, how likely is it that a Morty, without any training or experience, may disarm that thing? Remember, Morty is just a child at this point. A child with sub-par mental faculties, a lack of assertiveness and a lack of sleep. Oh, and he also has just a few seconds to disarm it (given by the noise the thing makes at the very end of the scene).
I tell you how unlikely it is, about as unlikely as the size of the multiverse!
That's right, I propose that one of the universal constants (those that are true for all universes) is Ricks self destructive behavior. That every Rick in every universe tried to destroy that universe. That is what makes a Rick a Rick. That is why Ricks and Mortys are scarce. Because every Rick that exists does so due to the fact that his Morty was infinitely lucky and managed to disarm that bomb (or other contraption). And deep down the Rick knows that. He knows that he needs the Morty. Not just for his brainwaves. But for his ever increasing talent to save him from himself.