Question: Why is order scoped to model properties only?

[pmooney-socraticworks]

From the readme:

The order option format only supports the ['field'] and ['field', 'DESC'] variations (field name and the optional order direction). For example, ordering by an associated model's field won't work.

I'm curious what the limitations are to prevent ordering on associated models' fields. I'd like to use this package, but this is stopping me from integrating it, and was wondering if it was a limitation of sequelize or something else.