The goal of DF is to be a fantasy world generator, for Toady.
Being a game one finds fun is second priority.
Yes, and a "fantasy world" is a world that contains stories. Stories are simplified, embellished, details left out or included, to make them [better]. This is close but not exactly the same to what makes the fantasy world fun. This is also close but not exactly the same to what makes the fantasy world
realistic. There's a kind of realism that means "complicated in a way that drives the plot and makes it seem plausible," and in that sense realism is always [good], but there is also "complications that are tedious and do not add anything to the plot or world", such as, ferex, needing to channel all information through a single dwarf. Would that make everything more realistic? Yes. Do you think that Toady will require the world to adhere to realistic communications on a dwarf-to-dwarf level? I don't. Similarly, some complications do not add anything to the story or world. These are a waste of time.
On the other hand, one could argue that statistically speaking, most realistic improvements are positive, so prejudice is likely to be positive. And the existing forms of rudimentary prejudice that exist are fine, so why not continue? This is a good argument and I have nothing to say against it. (However, this general argument can be overcome by a more specific counterargument; compare artifacts in Significant Digits.)
I mean, "average office worker goes about their day and works on boring and impenetrably specific trivialities" is realistic, but that doesn't make it
a good story. It needs something else, and without that thing, additions aren't improvements.
TL;DR: good world is one that makes good stories, good story is close but not equal to realistic story
Classic example: Wouldn't it be more enjoyable that if you embarked in range of goblins you'd be guaranteed sieges? Used to be case, but was changed in .40 to be more 'realistic' in requiring them to be interested enough, most interested and have enough numbers, with no toggle to change it back to how it used to be.
Variation is part of a good world. 'Goblins throwing themselves at your axe
ad infinitum' is interesting for the first few fortresses, but eventually the sieges get boring without some form of escalation. If they're rarer, they're more important. (every day can't be christmas, elmo)
Our world varies greatly. Thus, realistic improvements tend to increase variation. [similar for "challenge of finding enemy" etc.] I do not see that realism
itself is inherently positive.
Novel counter to above: You can now aggro the goblins anyway by raiding them, even if they find you boring. But that too has 'realism'.
If you choose something, and have to put effort into getting it, you value it more. Very little in real life comes without you working for it. Insert parallel argument from above regarding correlations.
Still, this is why we have unofficial "summon a siege" buttons instead of official ones.
In real life, we don't have labeled buttons for everything. Having to understand a complex world where you have to do certain things to trigger others is part of a good story, in a way that "Frodo pushes the 'destroy ring' button" is not. Ditto.