From a "this side of the pond" perspective, an ATP is really just the "commercial instrument" rating. The standards are those that are required for any type-rating, so anyone who's got 1500 hrs and is taking his Citation 500 or whatever checkride actually has to perform to the standard, so he might as well get the rating. The hard part is all of the part 121, 125, and 131 garbage you have to regurgitate on the written.
The instrument rating over here has been best described as a "license to kill yourself, but not the rest of us". Part 91 operations are nearly entirely permissive, in that there are no specific minima for attempting an operation (other than airport limitations) so some 200 hr pilot with his newly minted instrument rating and absolutely no actual instrument time is totally free to kill himself on an ILS to a 0/0 field.