The use of spotting scopes cover a wide area and is dependant on the match being shot, I feel.
Where they are allowed, it is up to the individual if they will use one, or not?
Common sense pretty much dictates when they shouldn't be used, and/or not
allowed to be used.
Competitors going to a match should be prepared for either. If spotting scopes are allowed and you want to use one, use it. If they are not allowed then you simply don't use it. Shoot the program the way you see fit under the club rules that is hosting the match.
Now with this said,,, I have shot in both type matches where they are and are not allowed. I'm prepared either way so it's no skin off my nose what the match rules call for because I'm there to compete regardless of the spotting scope rules...
The thing I don't like is where they are allowed - then folks show up and find someone who has a spotting scope and they want to share yours. To me this is unexceptable, but I do share, (and it's usually someone you know). Personally, I
did not buy my spotting scope 30+ years ago for someone else. I bought it for my use and for the matches I shot where they were and are today acceptable. I find this "leeching off others" when it comes to folks to cheap to buy a spotting scope unexceptable, but again I find myself sharing my spotting scope. It has even got to the point where these leecher's have actually asked,,, "did you bring your spotting scope?" Boy that's irritating to me...