It's definitely not a perfect system and you're absolutely right that it significantly favors people with strong support and safety nets, especially those of a financial nature.
That being said it's a very easy shorthand for a company to take and is reliable enough to keep using it, just like how financial institutions in the US use SSNs as private identifiers because it's easier and cheaper than running and supporting their own systems/assessments and mostly works well enough
The SSN system is one of the more moronic things the US does, which is really saying something.
