1) Due to it being a trend, it gets FAR more people aware and involved in the charity than would have been otherwise.
2) As a result of this, much more money is donated from people being a part of the challenge and those who simply are made aware of the charity. ($31.5 million dollars have been received so far from July 29 to August 20, compared to the usual $1.9 million.) SOURCE
3) If you really can’t deal with the fact it’s a bit of a gimmick for the sake of charity, you should probably re-evaluate your priorities.