Yes, there are people who show who are not breeders. There are also those who breed (and show) one particular breed but show other breeds as well. Education is one reason to show, but that is more important with the new breeds than with the championship breeds.
Showing is basically a competition. Every breed has a written standard, the purpose of showing is to determine which is the best Savannah, and how the best Savannah hold up against other championship breeds. Anyone can throw two savannahs together and register the kittens as Savannahs regardless of what they look like, however, if you are a breeder whose cats have earned championship titles then your kittens might be considered more valuable, and most assuredly have looks that are consistent, or at least close to the written standard. If you are not a breeder there is still reward in being recognized for owning a Savannah who has won championship titles.
Hopefully, those breeders who show and do not earn titles will take a closer look at their cats, figure out what is lacking, and make changes to improve their lines in order to come closer to the standard. So it is also a learning process for breeders as well. The competition can be addicting however, so even those who are not breeding may still campaign their cats in order to win titles.