The biggest challenge we face on weak days is being lured into
unnecessary searching turns. If the best you are seeing is 1-2 knots
achieved and the top of lift is low, you are probably being
conservative, chasing a fast vario more than is advisable. Having a
fast audio and a slower "averaging" needle lets you more accurately
judge whether it's worthwhile to turn. The slow needle lets you
extrapolate core size (is it wide enough to climb in) and the fast
audio helps to guide your centering.

(Getting used to pushing on at very low altitudes is another thing
altogether.)

This can be a valuable edge in competition. It's unlikely you will
outclimb anyone by a factor of more than 1.25 on a strong, consistent
day. But on a weak, low, blue day, a patient pilot can easily outclimb
others by a factor of 2 or 3 (achieved) by avoiding fruitless searches
for lift.