Using textbooks is very much frowned upon nowadays, for a variety of reasons.
First of all, textbooks are often almost useless and sometimes utterly useless. There are a variety of reasons - they're not differentiated for the very weak/very able kids, they're often far too wordy, they're dull as dishwater and they aren't pupil-centred. The older ones don't tie in with the curriculum; if they do, they're often one person's interpretation of what the curriculum should be and I don't always agree that their way is the best way to deliver it to my pupils.
I use textbooks very occasionally, but I'll supplement what I do with activities and slides on my SmartBoard, which allows me to demonstrate how to work through questions interactively.
Most schools seem to have entire schemes of work saved as SmartBoard files, with corresponding Word document worksheets and differentation - all produced by the teachers.
I can assure any parents who are reading that I spend hour upon hour planning engaging lessons for the kids in my classes. I have very good reasons for staying away from textbooks (not least of which being that I can't choose the ones my school buys), but to be honest I enjoy making SmartBoard schemes and would probably do it anyway because it works so well.
As for 'reinventing the wheel' - the schemes in my own department are used year after year. Designing a scheme of work is a big deal, and takes a long time - very few people would do it unnecessarily.
I'm surprised so many people are coming out in favour of textbooks. I hated mine when I was at school.