Not a lot of point printing the bus maps of the website, they are out of date! Not only are the printed maps history, but the online ones are yet to show fairly major changes such as the recent changes along Finchley Road. The response I had from TfL about printed maps cited cost and low demand as the reason. Money had been found, however, to print 14 new maps for cyclists, which they will also post out to you.
The reason the bus maps had low demand is because they were kept behind glass like a closely guarded secret. You had to know they exist to ask for them.
Out of all bus publicity, I find a map the number one thing that should exist in printed form, as you can't print them out yourselves. They give a good overview of the network and many operators up and down the country see them as being worthwhile.
I've always found the lack of printed bus timetables quite odd, particularly less frequent services in outer London. Whereas just over the border Arriva etc will provide printed timetables.