One can have many valid reasons for taking a particular photograph. It might be a subject which interests you. You might just think it's pretty. It may be something you don't even like but a client has hired you to do it. Maybe it captures a special memory.
The way you take a photograph can enhance or detract from the message of the image. Aperture, shutter speed, framing and all that. The choice of lens and focal length has a big impact on your final image as well.
There are all sorts of "rules" like the rule of thirds, placing open space in front of moving objects to give them someplace to go, etc but in the end it only matters what you (or your paying client) is happy with. I have many photos which would never stand up to a general critique, yet they are some of my favorites because of what they mean to me. I also get complimented on some images which I think are very blah, yet they seem to be the favorites of many others. Just this week someone who keeps an eye on the photos I post told me what their favorite image was (this one here). I chuckled at the choice because, while it was kind of a fun image to try, I wasn't happy with it and only posted it to show what I was experimenting with. I find the background too cartoonish (I used the euphemism "dreamy" for it) and that wasn't what I was going for. Of course, their opinion is every bit as valid as mine regarding that photograph -- they really enjoyed it. I've been reading through David duChemin's ebooks (which I recommend BTW) and have been thinking about some of these things in conjunction with his "Chasing the Look" ebook.
The handheld photograph above was taken in a dimly-lit Paris Metro station. I just love that picture. I love the lines, the composition, the slight bit of motion as the train started its journey, the green opposing the orange, and the darkness that waits at the vanishing point. Most of all, it brings back memories of a trip to Europe with my wife (we went all over on the Metro). As all three of my faithful readers will remember, this trip was about romance (cue the Ricardo Montalban voice for "romance") and not about photography, so my images were mostly about capturing memories. It may not appeal to everyone, but it captures all that I was after.