There is a reason, noise.
Giving an entire post with images that can be fairly tall real estate on the first post can be intrusive.
Imaging if the response on the 3rd post which is the accepted answer is:
Do this:
image 1 (640x480)
Do that:
image 2 (640x480)
Then:
image 3 (640x480)
Now the top OP will either have … 1 image which is not enough, OR 3 images which are enormous duplication.