From my experience the advantages of workbooks are:
The book “invites” the student to use it, it is more interactive, the clean and empty pages with spaces, are there to be filled.
The “theory” is introduced using strategies like: open questions, fill the blank etc. Never just “read the following…” The student must write something, cannot be passive.
The exercises are sequenced very carefully so that the level of difficulty increases slowly. It allows the weaker students to follow without getting lost.
The students keep the workbook at the end of the year and can use it in the years to come; many of my students even use them in the first year university course. They feel the book is “theirs” since they are the ones who wrote the answers.
This method can be applied to individual work, group work, homework etc.