A few people commenting this has not been their experience. It has been my experience in the NYC area. It could be a NYC thing. We have an abundance of taxi's so it very well could mean enough people just drop Uber and grab a cab instead. This would quickly lower the demand in an area.

It might also have to do with the density dynamics of NYC. Ubers are constantly going into and out of designated areas that surge pricing zones. It won't take long for a few Ubers to roll into the zone where there is a surge.

Things work differently in NYC due to the density and relative small area of Manhattan.