At periods of high demand the rate can be increased to help attract drivers to come out and become available to take a fair - it's seen as a great insensitive.
Furthermore, even if demand isn't especially great but there's a perceived low number of vehicles out (reducing their capacity to quickly react) it'll do the same.
Uber are meant to have cracked down on the cleaning fee, but apparently they can set themselves as 'off-duty' and back on-duty to help beat the procedures.
Personally, if I need a taxi I use them regularly now as it's easy to estimate a fare, track where they are and complain if necessary; plus, no need for cash!
