Where Ubuntu is seen to donate code back to the community, Xandros and Linspire have developed proprietary extensions. Where Ubuntu asks for manufacturers to free their drivers, Xandros and Linspire have signed patent covenants with Microsoft.
Being easy to install and easy to use is not enough. The first lesson of "open source business" is that your first debt is to your user and developer communities, from which everything else grows. OEMs will look first to the most popular alternative.