Ideologies? Rather doubt it....

Nokia has invested heavily in its production system, which relies largely on being able to use the same parts between different models as much as possible. They do not want to have 100 different chassis variants for the plethora of operators out there yelling for their own.

The companies most successful in the US market don't have this problem, for them it's completely ok to produce one exclusive model for one operator, as it guarantees them sales they wouldn't otherwise get. Competing like this would likely cost Nokia more money than it would gain.