My experience is that many do not post wristies because they lack (or fear they lack) the requisite picture-taking skills. After all, what is the point of posting watch pics that look like they are taken with the specific purpose of scamming ebay buyers. That is, small, dark & out-of-focus.
And for those of you who feel a high end camera is needed, you could not be more wrong. The vast majority of my pics are taken with a 10 year old 4MP Canon A80 point-&-shoot, & I think I get by. If you are unsure of your skills, please read Pugwash's outstanding (pinned) How to Photograph Watches articles. After letting Pug show you the basics, just practice taking pictures. That is the way most of us learned.
1 other thing - for every 1 great picture you see, it is likely (more than likely in my case ) that the picture taker took dozens of pics to get that 1 good pic.