First, a bondsman won't take the case if he thinks there is a decent flight risk. It's in his interest the accused show up for court. The accused also has family or friends co-sign the bond, and if the accused skips, they are on the hook for the full amount.

Surety bond provides a few layers of well, surety, that the accused will show up.

This is my understanding from sitting next to a bondsman on a plane a few years ago. He was on his way to CLT to deal with one of his bondees who skipped.