When I run a report, I can select a related module to use in the criteria when running the report. However, this does not seem possible when setting Conditions/Criteria in a Workflow Rule. Why?

I am creating a workflow rule on the Deals module. However, I want to also evaluate details/data from the Account that is associated with the Deal. But this is not possible from what I can tell. I am limited to only using fields in the actual deal record for conditions. Please allow workflow rules conditions to be able to evaluate criteria from related modules.