Python seems to be not too popular in enterprises till now compared to Java (but I believe the wind is in that direction. An example is Django, which was created by a newspaper company). Most programmers working with python are likely either into scientific computing or into web applications. Both of these fields relates to (computer) sciences, not domain-specific businesses, whereas DDD is most applicable within domain-specific businesses.
So I would argue that it is mostly a matter of legacy. C# and Java were targeted towards enterprise applications from the start.
