Discrimination is around things that an individual can't choose (religion being the weird elephant in the room). Fair or not, this isn't discrimination.
In the UK, the Equality Act (2010) protects: age, disability, gender reassignment, marriage or civil partnership (in employment only), pregnancy and maternity, race, religion or belief, sex, sexual orientation.
Pregnancy, maternity, marriage, civil partnerships and gender re-assignment are usually chosen by individuals, not forced upon them.
Many people can’t choose where they live either. Getting a visa to the US is a ludicrous process and even if they wanted to they maybe tied by family obligations.
But people don't choose to be rich or poor exactly either. As a general rule, discrimination is around things for which there's no choice. Having a choice over where they live or whether they are rich doesn't mean it's easy or practical. But that can't make it grounds for discrimination, even if unfair.
Pregnancy, maternity, marriage, civil partnerships and gender re-assignment are usually chosen by individuals, not forced upon them.