Provide multiple column Join functions and different Join cardinality

Why can't power BI have the same capability as SQL for joining tables, i.e. be able to do left / right / full joins using multiple columns as relationships?

It seems like Microsoft have restricted the join capability to make it simple for the users, however what happens instead is that people need to do complicated work arounds to achieve what they need to do - e.g. by making a concatenated column to join multiple fields together in two tables.

YES - This is a must! This is a very common use case and should be basic functionality.

SAP BusinessObjects has nailed this functionality with their universes.

This would also be great to have joins based on an OR function. for instance joining a table used to implement RLS to a fact table (f) where the user(u) is either the salesperson or the engineer for a customer: u.userId = f.SalespersonId or u.userId = f.EngineerId. Functionality to join tables on moren then fact.key1 = dim1.primaryKey should be possible.