Writing can be entertaining, informative, educational or any combination. It can be funny (my preference), thrilling, horrifying and show you worlds on this planet as well as show you worlds the authors invented. Good writing keeps you gripped, no matter what format it is in. Good writing makes you think. And it is lovely to think that somewhere in the big library of literature out there, your own works make their own contribution to that library.
Taking you out of yourself...
This is particularly nice when life is on the grim side. Writing can be therapeutic, escapist and by thinking on something outside of whatever the problem is can be a worthy distraction. I've also found if I'm not thinking about a problem too hard, I'm less fazed by it. And if I don't get an answer to my problem by thinking about something else (my writing), I usually end up with more story ideas at least. So there's nothing to dislike there...
It's fun (and as yet the government haven't taxed it).
Two excellent reasons to write!
The sense of achievement when a story comes together...
It is hard work to write a short story, yet alone a novel, but if you manage it, whether published or not, you know you have achieved something special. The number of unfinished stories out there must be in the several millions range. At least yours isn't part of that. And if you can get it published online or in print, even better.