The PTS for the SEL rating requires the demonstration of steep turns,
and this maneuver is flown on virtually every check ride. I believe
that the main reason for "gentle" turns is a cultural and training
issue. Power training almost always considers the passenger in the
aircraft--something which is normally not a major issue in soaring.

Frankly, most true passengers are not comfortable in bank angles
greater than 30 degrees. A second MAJOR issue is the continuing
training toward the instrument rating. In actual instrument
conditions turns are normally accomplished at "standard" rate--a
gentle bank. This provides less chance for the pilot to loose control
while flying only with reference to instruments.

An often heard comment from the CFI during the training of a
commercial student is that when he gets his first commercial job his
performance will be judged by the smoothness of his landings
(regardless of winds, etc) and not spilling the president's drink in
the back.

Just some thoughts--

Skip Guimond