Today's fabric is not made as it was 'back in the day'. Almost every shift at work, I will have a fabric that I have to cut straight, but the pattern is off. I usually add a bit (and then write the couple inches off as damaged) so the customer has the option of cutting with the pattern or the grain. Personally, if the pattern is close, I don't worry about the grain and if it is really off, then I will purposely cut weird (like a bias cut).