> People who are guilty of driving while black, or non-violent drug offenses, or so on, are given much less generous treatment when it comes to unsecured bail

There's several factors at work here, but the most significant is that most offenders, especially most low-level offenders, are charged in state systems, and most (but not all, and this is changing, erratically) of the state systems rely much more heavily on financial conditions, and on secured bonds as the primary condition, in part due to very intense lobbying by the bail bonds industry to state governments (both directly and using astroturf groups to lobby the citizenry when their position is threatened.)