A key purpose for langar was to challenge the prevailing caste system — people of all castes would be equalized by sitting together and sharing a community meal, a revolutionary concept.
It's still revolutionary to sit down with people you don't know and share a delicious meal. Sitting on the floor is something we don't do all that often in the West, so IMO, that also opens one's eyes to a different perspective. Langar was and still is revolutionary!