This. It's extremely common for blades not to be perfectly brazed into the crown, or tweaked so that identical adjustment just isn't possible - though one can selectively bend the blade with a Park FFS-1 to get them closer to each other.

It's also absolutely imperative to cold-set the dropouts with a pair of adjusters as well; bent dropouts on a straight fork will shift the wheel's position regardless. Granted, sometimes even after all the possible straightening, the wheel might ride cockeyed in the fork. At this point, I file the dropout on the side the wheel tilts to - but ONLY IF I am 100% certain that I have the blades perfectly aligned with each other.

Also, as crazy as this sounds, if a fork is obviously twisted but not directly bent to the side, sometimes one can get away with putting a dummy wheel in the fork and then using the stem and bars (provided the wedge is strong enough to prevent slipping) against a wheel held between the legs to bend the fork straight again. I don't always recommend it, but on a fork which is twisted only, this can both re-bend the blades and the dropouts perfectly back into their original location. Again, this has very limited applications, and only works if the force that caused the bend was the exact reverse of your twisting motion to straighten it.

-Kurt