One of the reasons is that they break down reasonably complex issues and make them really simple to understand.
Like this, for their September campaign.
Really clearly laying out the problem.
And clearly setting out the campaign goals.
The campaign is supported just as beautifully online.
Charity: water get a lot of attention from fundraisers in the UK. There's a lot of admiration for how they interact with their supporters and how they present the messages they want to communicate to the public. So much so, that it seems it's becoming a bit of a cliche to mention them. But to be honest, if the quality of work is this good - I really don't care.