In answer to your "Why?" question:
1. It's light - very light. That's the reason I bought one. In the summer, going to events that require dress slacks but where there is no need for a jacket, the only logical option for me has been the ankle holster. For ankle holster wear, the little 317 has been perfect. Doesn't feel like a boat anchor tied to your foot.
2. Eight shots - not 5, not 6, but 8.
3. No ugly hole or associated components.
4. There is no one I know who wants to get hit in the face with even one round of hi-speed .22 LR - and seven more shots are there for the asking.
Check the picture above. Notice a couple of things different from yours?
A. The optional factory Dymondwood (laminated wood) stocks - more than a tad lighter than those Goodyears.
B. The hammer is different, too. Like you, I despised the DA trigger pull. I complained to S&W customer service, and they had me send it back to them. They installed a Ladysmith hammer and spring. Made a noticeable difference. Recognize that with such a small handgun, the hammer spring has to be pretty stout to throw the light hammer with sufficient power to assure ignition of all the various makes of .22 LR. While lighter, the Ladysmith arrangement will still give reliable ignition for
most .22 ammo out there. Test it with what you intend to carry, and if it fires every time, you're good to go.
Hope this helps you re-think your purchase. It's a great little gun, with purpose-built features.
John