No abdominal work in a program?

In some programs, there won’t be direct ab work. The reason is that you're getting substantial indirect ab work from the multi-joint compound movements. The training volume is better dedicated to other major muscle groups that require the extra volume.

That being said, if you prefer – or if you simply like doing some abs at the end of each session – feel free to do that so long as it doesn't impede recovery or burn you out.