All concrete cracks a little. The goal is to make it crack where you want it to, in a straight line inside a control joint, and not to crack because the ground underneath moved. In Miami, GA, the ground is usually the problem.
Much of the area sits on sandy clay and soft soil that shifts with our heavy rains and humid summers. Loose sand settles, and fill that was dumped and never compacted settles even more. When a slab is poured on top of that, the weak spots sink, and the concrete above them breaks. That's the wavy, random cracking you see on old driveways around Turner and Ben Hill County.
The fix happens before the truck arrives. We dig out loose material down to firm ground, add base where it's needed, and run a plate compactor over it until it's solid. Then forms are set to grade so water runs away from the house instead of soaking in at the edge of the slab.
Control joints handle the rest. Concrete shrinks as it cures and expands and contracts with Georgia's hot summers and cool winters, plus the moisture swings that come with them. Joints spaced at the right distance give that movement a straight, planned place to go.
If you're comparing estimates, ask each contractor how they prepare the base and how far apart they space joints. The answers tell you a lot about how the slab will look in five years.