TL;DR because the Constitution was written to protect us from the government, there is a lower bar to sue and win under both federal law and constitutional challenges.

For example, the Fourteenth Amendment protects against discrimination by States, not private actors: https://www.law.cornell.edu/constitution-conan/amendment-14/...

And note 1338 calls out that the federal laws prohibiting businesses from discriminating against individuals are instead rooted in Congress's broad latitude to regulate interstate commerce.

And here's another similar reference:

> As a general rule, the Constitution does not give power to the federal government to pass laws to protect people against private actions. For example, the Equal Protection Clause guarantees equal protection for all – it protects against discrimination. Under this protection, the federal government may pass laws to enforce this guarantee. However, while Congress may pass a law to regulate states or other public actors, it may not pass a law to regulate private citizens. Your police department cannot discriminate against you on account of your race. However, your neighbor in the house down the block can be as bigoted as he so desires.

https://constitutionallawreporter.com/amendment-14-01/the-qu...