They accept much lower margins than Apple, in part because Apple is notorious for pushing its suppliers for lower prices to boost its margins.
I buy Samsung phones because I know they treat their workers very well for the most part both in Korea and abroad. In Vietnam, they built daycare, hospitals, school, park, housing for the entire workforce. In Korea, they give out huge bonuses to workers and will promote talented people.
I also buy Samsung for the same reason I buy Hyundai, it's not that I can't afford the more expensive brands, I do it out of patriotism for the motherland and scream "TRAITOR!" with the windows up when I drive by a Korean person in a Subaru.