That assumption holds for most of the population in European countries, even the poorest ones. In fact it's common for young people to live with their parents a long time.
One has to be either dirt poor or very unlucky not to he able to move back with relatives. This sound like an excuse.
The median wealth of African American households in the U.S. is $35k, vs. $150k for white households.
Yes - most people might be able to move back in with relatives, but among those people who can't, minorities are almost certainly going to be overrepresented, which was OP's point.
One has to be either dirt poor or very unlucky not to he able to move back with relatives. This sound like an excuse.