GranB - because it is good for children with Down's Syndrome to be shown in a positive light. The firm needed models and for once they did not look for the 'perfect' version. Please note my quotation marks, before anyone jumps in and accuses me of saying that Down's children are not perfect.
For too long Down's children have been written off - in some countries which devote enough resources they have a huge success rate in literacy.
I have been very heartened by the use of some young actors in recent TV plays - they are very talented and I hope casting directors will continue to use them and help to improve the public understanding of the condition.
I know that many children with Down's also have other health problems, but we are finally beginning to concentrate on what they CAN do, rather than on any limitations.
Emmerdale is doing a good job with little Leo - such a storyline would not have been handled even twenty years ago.