[SmG Phoenix]

A rather scifi fantasy alternative is that we live in a matrix-esque simulation, in which nothing outside our perceptions is really tangible- there would be no aliens because there is nowhere for them to actually be.

Think about it like a video game. A video game doesn't load it's entire contents at once. It loads it in sections. The problem of why there seems to be no observable intelligent life could easily be solved by saying "well, there are no planets outside of what we've physically observed with our eyes/tools anyways". The light from all the other galaxies and stars and what not could easily be thought of as a simple skybox- a flat, 2-dimensional image meant to simulate the idea that there is something beyond the chunk we've forced the system to compute by observing it. The catch is that the universe could have instructions for these other zones, but because we haven't observed them they simple haven't loaded. To put it simply, the ayy lmaos can't make first contact because they don't exist until we force the "game" to load them in.

As for why, well I would imagine that if this is a simulated universe, the amount of computational power necessary, even for our relatively small zone, would probably be some sort of Matrioshka brain. There is probably many different universes and worlds being run simultaneously if that's the case. You wouldn't want some infinitely expanding system to compute everything within it, obviously.

I really like this idea.
Heat death aka Deep freeze theory here?