All these years later, nothing much has changed. Homebuyers still expect a certain level of quality, and because garage floor cracks are so visible, they often think that cracks reflect low quality. Garage slabs are generally built using one of two main types of construction: 1) placed monolithically with the main slab of the house, incorporating a 4”stepdown or 2) placed separately, usually using a concrete masonry unit (CMU block) or concrete stem-wall as the edge form. Additionally, there is a regional, popular use of CMU “form-blocks”. Naturally, these form-blocks, just as any stem-wall, are set/bonded directly onto the footing.
Anything we can do to allow independent movement of the concrete slab, allowing it to shrink/move from all directions toward the middle, will help eliminate random drying shrinkage cracking.