My responses to this question are many and varied. In this post, I'll touch on just a couple in addition to what I shared earlier in Part 1.
As blunt as it may sound, I write because I have to write. A day without writing is a day void of joy and pleasure. I never realized this until after retirement, at which time I thought, "I never want to sit in front of a computer again!"
How wrong I was in making that statement. The sitting in front of a computer that I'd been doing for decades was to type pleadings in a case for an attorney, or to draft up legal documents. It wasn't writing for the pure joy of it.
Now, I write because I want to, I enjoy it, and yes, I have to write. And now you're next question likely is why do "I have to write."
And the answer to that is that I have a story (perhaps more than one) that either needs or deserves telling. No one can tell that story but me because it is personal to my life. Others created through my imagination will also be mine to tell.
If I don't write, will they ever be told? Likely not. So, I write. I write something every day, either on my work in progress, a short essay or story for a competition or in answer to a call for submission, or for one of my blogs.
Do you have a story or perhaps stories to tell? Are you writing them down? It doesn't mean that you're striving for publication, but perhaps just leaving stories for your children and grandchildren to enjoy in the future and pass along to others in the family.
Think about it . . . try it . . . you too may find joy in writing.