Look up your default rates according to race and you'll have your answer as to WHY certain races are discriminated against.
I’d venture to estimate that poor Whites are probably turned down at a rate close to that of Blacks.
As you point out, it’s about ability to pay, not skin color.
It also has to do with certain areas, the elevated crime rates, and the number of failures in that area. (at least, I suspect that also has something to do with it)
Some will call this redlining, or use some other term.
Sorry, that is entirely reasoned. People who loan out money want to get paid back. Imagine that!