A weed is a weed, not a flower growing in the wrong place. If a specimen of the Bluegrass' delicate Rose Gentian showed up in my perennial border, I'd move the gladioluses. They thrive when vegetables don't because we've selected them, just as we've selected the vegetables. Centuries of pulling, mowing, tilling and mulching have ensured that only the toughest weeds survive. Tomatoes are more vulnerable because we've singled them out for special treatment, watered and fed and coddled them through conditions that don't bother curly dock.
Dock is a good example.
Its tall, coarse brown seed heads cover those bulldozed sites awaiting financing for new strip malls. Natural vegetation doesn't wait. However, many diverse seeds brought by the wind will take root if they're capable of growing there. Dock grows on hardpan because its 18-inch taproot, amazingly, pierces subsoil, making nutrients accessible to a later succession of plants. Not too long after dock, clover appears.