When they are made, a flat piece of wire that will serve as the ground electrode is welded to the threaded casing. Another machine comes along and bends the wire over. At the end of the assembly process, a few plugs from each batch get measured. If they pass, so too do all the other plugs in the batch.

If you've bought new plugs and have to re-gap them, make sure your ground electrode is parallel to the center electrode's face. If it's noticeably angled, I'd go and get a different set/brand. The bend in the ground electrode won't accommodate your gap. They'll still work, but the gap will grow quicker with use. This isn't common and could mean you walked out with the wrong plugs.

And if they are bent because they were dropped, I'd still go back and get another set. Even if you did it, just buy another plug and own your mistake. For a few bucks, it's not worth the risk of installing a plug with a cracked ceramic insulator.