" because IGC rules encourage longer tasking that use up the available day...."
Because the US rules seem to favor (and often result in) AAT's with very large circles..."

Minor correction: There is NOTHING in US rules about short tasks or large circle AATs.

"10.3.1.3 Normal Task - Tasks should make as full use of the available soaring weather as is practical"

Appendix: "- Try to use the full day, not merely the best part of it.."

The TAT appendix suggests 8-10 mile radius and 15 miles for the final steering turn.

Short tasks and few enormous turn areas rather than a larger number of smaller turns are choices made by the CD and task advisers, often in response to pilot complaining. If you want the opposite, talk to the CD don't complain about the rules.

John Cochrane