Though, you could say it's indirectly designed for beauty. When astronomers process an image, they are looking for interesting features to study. And once you've narrowed in on the most scientifically interesting way to process an image, the sorts of striking color contrasts that creates are inherently beautiful because they are unveiling the interesting parts & letting us see the unseen for the first time. And there is selection bias on what is interesting to look at. A violent explosion is both more aesthetically inspiring and teaches us more about how matter works than a picture of a random stairwell, and astronomers love their violent explosions.
That being said, the complaint that the images are "unrealistic" are off-base. The images accurately portray the information that was captured by the telescope. Your eyes often can't even see the wavelengths imaged by space telescopes (like the James Webb Space Telescope), so how you map those wavelengths to RGB is largely arbitrary. As long as you map them in the same order (shorter wavelengths appear bluer, longer wavelengths appear redder), I would consider the images accurate.
It is true that they also look at a lot of grayscale images, though. Differentiating chemicals in nebulas or on the surface of planets isn't always necessary, and you can always take the simpler (but sometimes less useful, since it doesn't make full use of the human visual system) route of looking at multiple grayscale images. A lot of the areas where false color is most useful are well-trodded ground, so we don't necessarily need more images of the same objects when the existing body of research is already rich. And sometimes, a researcher includes an image in their paper just because they thought it looked cool, not because it was useful for the methodology.
There are some rare cases in which an audible might look at a color image, but the overwhelming majority of images astronomers deal with daily are grayscale.
A screenshot of this page would capture a title bar in orange.
The REAL title bar is displayed as dots of green, blue, and red; no orange is present.
Would you rather thaw NASA show you a blank image and say, "This is our newest infrared image from the James Webb Space Telescope!"
They map the images into wavelengths you can see. There's nothing else the can do, other than not showing you the images at all.
There are edge cases in which astronomers will load up images at multiple wavelengths and overlay them, but this is not the normal case. By and large, they're looking at a single channel at a time. Even more commonly than that, they're working with catalogs automatically generated from images.