I think some of the pattern makers are lazy and don't want to go to the trouble of calculating from yardage as well. The only pattern I ever bought had an offhand reference to using yardage, but It was so vague that i ended up drafting it and doing all the calculations from a jelly roll to yardage myself. I think that if you are a well-known pattern and fabric designer and can make plenty of recurring income after the work of putting out the pattern is done, you should a) check it for errors and b) take an extra hour to make the pattern accessible to the people who aren't buying your jelly roll.
JMO,
Charlotte