I never just compose a post for an OP. I also write because it feels good to write.  I enjoy the process of thinking about something and conveying those thoughts somewhat intelligently. Writing also helps me practice my communication skills.    In addition to the above, l reply to OPs so that others may hear what I have to say. Maybe my words won't reach the OP, but there is always the chance they could resonate with a lurker who is going through a similar issue.