The answer in truth, is they really don’t. If a judge grants bail for the defendant, they are under no obligation to have to pay for it or pay the 10% to a bail bondsman. Bail is merely the opportunity for the defendant to be released from jail while they await their court date.
Most people would rather be released from jail than have to wait in a jail cell until their arraignment. This also gives them time to get their personal items in order, get an attorney, public defender or legal team, take care of work or school issues and provide for child and family issues.