But My Epoxy Garage Floor Paint Kit Says That Etching Is Not Required...

With some possible, rare exceptions, etching isn't really a requirement for epoxy garage floor coating so much as a strong suggestion. However, if you're wanting to guarantee any decent amount of life from your epoxy, and your kit tells you that it needs to be done, then you should definitely etch your concrete. The main reason for this is that smooth concrete will prevent epoxy paint from creating the seal that keeps it from peeling. There are some kits out there that advertise that their product does not require etching, but that's a bit of a lie by omission. These coatings aren't meant to last long and, many times, etching is still mentioned in the instructions as "strongly recommended, although not necessary", or something similar.