In loyalty programs the benefit percentage often increases as a function of money spent, disproportionally benefiting the more well off who spend more. I've yet to encounter a loyalty program that would do the inverse (probably there are some that cap the benefits, which could be interpreted to be to this direction). Neither have I seen a loyalty program that would only accept poor people.

Price discrimination is anything where the same product is sold at different price for different buyers. All loyalty programs are price discrimination.