Customs body mounts

While I certainly understand the need for body mounts, a little confused over placement. Many (most?) cars I've seen have mounts extending off the frame, usually in the corners of the frame. Is there a reason why the mounts can't be sandwiched between the frame and body? Thanks

 

The ones on my old (don't have it anymore) were. I did one of those unmentionable frame swaps because the stock frame had too many cracks in it and just flat needed way too much work. I used Tri 5 motor mount biscuits for the body mount cushions

 

I can offer a couple of possible reasons most body to frame mounts are not between the body and the frame.
1) If the frame is boxed, you have to have an access hole in the bottom of the frame to put a nut on the through bolt making it difficult to install the nut and a washer if needed. Or the through bolt has to p*** entirely through the frame so the nut can be added on the bottom. This could cause the frame to squash together and possibly allow the body to shift and move. One would have to sleeve the through bolt to prevent this, which would be much more complex then just making a big hole in the bottom for the nut/washer.
2) A bracket added to the side of the frame for a body mount would make it much faster to add the nut/washer on the production line.
3) With the mount between the body and the top of the frame, the top of the frame carries the stress. With a bracket welded to the side of the frame, the top of the bracket carries the stress. Its easier to fix a stress cracked bracket then it is to fix the top of a frame. Gene