Most of the complex accounting and legal questions that these departments are doing manually aren't completely trivial either (we are not talking about just adding assets). But the determination of whether the paper on the floor is trash or not is something that pretty much any AI professional can apply his mind on (and will likely do given the size of the market), whereas very few will apply their mind on how IFRS should treat a tax asset in consolidation when the corresponding tax treatment under USGAAP is a still in discussion.

If you look at self driving cars, they are already doing the sort of wizardry of your trash example when analysing the other objects in sight.

And again it's not so much a matter of technical complexity, it's a matter of the domain being inaccessible to those who can best automate it.