Basically, these guys were/are nutters.
There is probably some Koranic injunction against equipment. Further, I don't think the mechanical skills and arts of Muslims is all that high. These aren't Germans.
Actually, there’s the whole “as Allah wills” thing in the Koran. Basically, some of the Islamicists believe that the wearing of armor is evidence of lack of faith in Allah - for if you are doing Allah’s will, surely Allah will protect you and none of the infidel bullets/knives/swords/arrows will hit you, right?
My ancestors had a *field day* with that particular idiocy when Islamic armies came against us.
As I recall, the number of books written and/or published in Arabic worldwide averages around 14 a year.
That's outside the Koran, of course.