It isn't the steep banks the make parachutes the norm. It is the 1 or 2
other gliders in the same thermal less then 200 feet away not being
that uncommon that makes the parachute the norm.

Also if you ever fly a contests, then parachutes are required by the
contest (usually) and if you have a $1000 parachute it seems kind of
silly to leave it home in the closet. Especially when most gliders are
designed to accomodate the parachutes.

Brian