A certain small percentage of normal people can have loss of blood flow in certain arm/neck positions..

I am one of those people, I could hang by my arms and do kids stuff just fine , but as I got into my 20s ( repetitive job ) I had trouble when holding my arms up for more than a few minutes. Found this out when remodelling our home..often had to hold something up so dh could fasten it , and if he wasn't fast my arms went to sleep and got heavy..

If you happen to do those positions often or in a repetitive job environment, it could become more problematic. It was for me..

Upper body posture is a good thing to practice & work on.
some easy basic things -
http://neurotalk.psychcentral.com/album.php?albumid=422

If you can avoid surgery , that is the best way, but often some expert PT , chiropractic or bodywork is ended to get you going forward properly.

Surgeon have to have a fairly clear reason to move forward requesting a surgery, so that is probably why , you aren't in a bad enough state, and really you don't want to be there if you can avoid it.. often it is not a fix all 100% thing... scar tissue, other pain issues...can come into play...