In my subject area, I don't think there is a great need for traditional textbooks. Diagramming sentences and the study of grammar has been proven to have no impact on improving writing ability.
A literature book with short stories and poems is a helpful resource, but I never see myself using it from start to finish. Of course, I think novels for students are the most appropriate "textbooks" to actually check out to students.
This has been a wrestle with my department last year and this year. The long-timers in the department insist that all students should have a literature and language book checked out to them all year and to require students to bring them to class daily. I fail to see the educational value in this practice, so I didn't check books out to my students. And it didn't go over well.
There are so many resources and more current texts out there, I hate to be tied to the regiment of a dated textbook.