It is quick. This compares favourably to normal book production. In book production you have to have 500 to 1000 copies printed at once. This demands considerable initial financial outlay. It is slow, taking about 6 months.
Colour printing is expensive.
The bulky books have to be stored, then sent out to readers. Packing and postal charges are high. You don't know if you will be left with a large number of unsold copies. In later editions it is tedious to insert corrections, additions and then print off 500 more copies. With CDs you can go carefully.