It is to strengthen Shmiras Shabbos. They sing songs (“heilige Shabbos…, etc.), have shmuesen by rabbonim about Shabbos, etc. as they march across Kings Highway. It’s been done for over 50 years, one Shabbos each year, and was started by a number of gedolei rabbonim. In the early years there were Jewish owned businesses on Kings Highway that were open on Shabbos r’l, and the Shabbos Parade was B”H successful in encouraging a number of those stores to close for Shabbos.
Meno – Boruch Hashem, I have lived most of my adult life in EY! And even when I lived in chu”l, it was mainly out-of-town. I was just proud of myself when I finally figured out that Boro Park and Flatbush are sections of Brooklyn, and when I found out what the five towns are.
Now, if I could just figure out the streets in Yerushalayim.. The fact that I don’t know that is definitely a cause for shame!