Like their parents, Jewish Young Adults hold a variety of beliefs about keeping kosher; some are strict and will eat no dairy from an animal that was milked by a Non Jew, others are mildly observant and will eat dairy with chicken, but will not touch ham or shrimp, and others are completely lax to the point of consuming bacon shakes.
Each spring, however, JYAs eschew the Steak ‘n Shake during the commemorative holiday of Passover. Kosher for Passover is a stricter prohibition, added on to the usual rules, wherein Jews cannot eat leavened bread—bread that rises—because when the Israelites left Egypt they did not have time to let the bread rise.
Each year, Jews are encouraged to remember leaving Egypt as if it had happened to them. Thus many JYAs, including those of the laxest possible faith, spend the Passover week carrying around a box of kosher for Passover matzo, dramatically refusing pizza and sandwiches saying, “Sorry dude, I’m keeping kosher for Passover.” To a Non-Jew, this phenomenon is roughly equivalent to Christian girls of loose morals giving up fellatio for Lent.
In no other area is there such a contrast between Diaspora behavior and that of JYAs in Israel. In some areas of the Midwest, the village Jew will be forced to scrounge up the one stale box of matzah in the international food aisle of Meijer and make-do for the Passover period. The Tel Avivian JYA, on the other hand, can order his McGriddle on a Kosher-for-Passover bun. Rather than having to pull a slab of matzah out of a paper bag and swallowing the dry bolus with massive quantities of water while her friends are eating out, the Israeli JYA can safely assume that everything on the menu is kosher for Passover unless otherwise stated.
By keeping kosher at this specific time, regardless of their conduct through the rest of the year, JYAs can best earn the sympathy of their Non-Jewish friends for the centuries long plight of the Jews and impress them with the more bizarre and stringent aspects of their usually low key faith.