What is the benefit of not returning anything for commands in the CQS pattern?

It's clear to me that performing some kind of modification to the underlying data when I do a "query" in a class would be misleading, like making getMyValue() do some kind of side effect. That would be difficult to reason about. But if I do some kind of update like updateModel, I don't see the problem with having it return a query, such as returning the correct state of an entity. I would assume that an error in the update would cause an exception to be thrown. Not returning any values just makes extra work to do a query.

What regrets would I have if I return values with commands in CQS?