Observant Jews see to it that everything they eat is kosher, pickles included.
The same reason as anyone else does.
One of the commandments of Passover is "you shall eat it with unleavened bread and bitter herbs" (Exodus 12:8, Numbers 9:11). Lettuce can be extremely bitter if you let it bolt. Bib or iceberg lettuce would be a bad choice for a Passover Seder. Romane lettuse, however, can have a strong taste, and if it's picked late in the lettuce season, it can be really bitter.
Kosher foods.
They are made according to Jewish law and custom, and in cleanrd facilities(never touching what un kosher food has touched)
They do if they're Jewish. Not if they aren't.
if it's kosher
That depends on whether you're Jewish. Pork is not kosher, so if you're Jewish it's not kosher to eat it. But if you're not Jewish then it is kosher for you to eat anything you like, so long as it didn't come from an animal that was still alive. There are some traditional Chinese dishes that are not kosher even for non-Jews, because the animal is eaten alive, but pork isn't one of them.
You may be thinking of kosher. If so it's what a Jewish person can eat. (meaning if it's not kosher, they can't eat it)
Liver
No, moose isn' kosher.
They eat any kind of meat except for pork. However, it MUST be kosher.
Non-kosher pickles usually have the same ingredients that kosher pickles do only they're not made under kosher supervision and the ingredients used (vinegar mainly) might not be kosher.
Foods that Jewish people cannot eat are known as 'non-kosher'.
Jewish Germans eat kosher food. Like in other countries though, many products that are sold in grocery markets have kosher certification.