I'll go counter to most opinions here too: I think it can be a nice milestone for the dev, something to look toward and give some fresh air from the development of the main game.
Ideally it requires less work, might be more linear or more of a wink and a good excuse for some fan service. Like, I don't know if the dev of LongStory short wanted to explore more in depth that Alex girl (the Instagram one) even if it is not yet a playable path I wouldn't mind (wink wink in case the dev sees this).
The Halloween special tends to show chars in a different outfit and some light themed fun.
I by no mean need those events but if the dev likes to make them by all means I'm happy to play and explore them (especially if I happen to be on that holiday).