Its a very difficult sport to learn and it requires a lot of coordination. You can't just be a hack and get good. Takes a lot of time and dedication. So, impatient, low intelligence type people aren't able to comprehend it. Answers isn't really going to help you figure it out.
I might ask why do people like football (or soccer if you prefer). That bores me to tears too. At least tennis players have to use their HEADS - more than can be said about some other sport.