Why are there no Reapers in Andromeda?

You keep conflating different parts of the programming. In a program designed to create a solution, there would be a base data set, a problem statement / definition, and then the processing logic. At least, that's how computers as we know them today work. Logic needs something to process, whether it be a database, user input, or a message from another automated process.

The base data set would presumably include what the Leviathans know of the Milky Way and its history. We know that the processing logic allowed the AI to gather additional information, because it did do a lot of experimenting and researching throughout the galaxy. And the Leviathans are very clear about that scope:
"Before the cycles, our kind was the apex of life in the galaxy."
"You cannot conceive of a galaxy that bends to your will."
"It created an army of pawns that searched the galaxy, gathering this data."
"The galaxy itself became an experiment. Evolution its tool."

The Leviathans pretty much flat out tell you that the AI never went beyond The Milky Way.

Which is untrue. The Reapers leave the galaxy after every single cycle. They hang out in dark space. for tens of thousands of years. More than enough time for them to visit nearby galaxies and return.

The reason why the reapers were defeated in this cycle is because they were made stupid.

Well, I guess you can (and apparently will) make up whatever you like about the reapers.

You keep conflating the problem with the solution. They're not the same thing.

If I wanted to plan a party to host 20 people, there would be many possible solutions, and different ways to think outside the box in creating that social event. If I changed the guest list to include 200 people, however, the same plans (like the venue selected) might not work - because I've changed the scope of the event I want to plan.  A different problem (hosting 200 people) would require a different solution.

The Leviathans were concerned only with life in this galaxy.  The AI had the freedom to think outside the box in creating a solution (at any cost), but we have no indication that it was empowered to change the problem definition (including the scope).

Guys, I don't know why you are having this argument. I answered the OP with the correct answer which negates this argument. 
Lets think about it logically step by step. 
Pasqaule said: 'We know the Leviathans are stuck in this galaxy. But we also know the Reapers are not. This galaxy could be one laboratory experiment of many.'
So lets say the reapers perform this experiment in 10 other galaxies, what about the hundreds of other galaxies in our local group? By the same argument, why be limited to 10 galaxies when you need to control variables outside this new experiment.
Lets say the reapers control all the galaxies in the local group, what about the other hundreds of millions of galaxies (probably more) in the one universe. 
Lets say the reapers control all the galaxies in the entire universe, what about the infinite number of universes that exist in our space time?

The reapers cannont be infinite because the universe is only 14 billion years old and it would require an infinite amount of time to have an infinite amount of reapers. Therefore that premise fails.Therefore there must be limits put on the scope of the experiment to make it achievable and not an impossibility, otherwise the mandate to protect organic life will never be achieved.




Therefore you must always have an experiment in which there exists outside variables uncontrollable by the catalyst. There is no evidence to suggest that this experiment exists beyond the milky way based on available data. Therefore the reapers existing in other galaxies is only a supposition and has no real weight behind it and cannot be argued until further evidence to the contrary is presented.
Otherwise you undergo a tangent of unhelpful arguments with no basis.

Like I said awhile ago, the Leviathans are very specific in telling us:
1) Their area of concern was the galaxy, galaxy, galaxy, galaxy.
2) The AI / reapers confined their research and experimentation to the galaxy.

You can take what's presented in-game at face value - or not.

And I knew I'd regret providing an example of scope creep.

That depends on whether or not the reapers have the capacity to assemble two entire networks across 2 galaxies in this timeframe. Frankly, their being grossly overpowered as they were got old. Being able to totally occupy two galaxies and build what would take eons to establish is pushing it. At this point, trying to stick to any hard logic regarding the reapers' sphere of influence is kind of meaningless, especially when the whole cyclical extermination bit doesn't really hold up that well to serious scrutiny either. This narrative just has little to no worth since BioWare pretty much played all their hands by the end of the trilogy. 

But, since we're on about this, it does get me wondering about the implications of reapers occupying Andromeda. Presumably, the catalyst would have some sort of means of communicating with the Andromeda reapers, and if these MWborn killbots were taking control of 2 galaxies, it stands to reason that they would create a bridge between the two so they can stay connected and minimize time to transport assets. They wouldn't futz about with a longer trip once they got to the other side.