Whoever mentioned American Football - you might have a big following in the US but don't you think it would be that much bigger if the rest of us could 'get' it?
That's where tennis has a problem.
American Football actually has quite a decent following in the UK, and liking it or not liking it has nothing to do with "getting it".
I'm sorry, but there is not a single sport out there that is remotely hard to follow once you've either played, watched, or read about the sport for just a very very short while.
Whether you end up liking the sport or not, is another matter. But it has F all to do with the scoring.
The game of tennis has no problem at all. It is a good sport, enjoyed and played by many. The problem with the sport are other factors besides the rules or structure of the game itself. People wanting to make stupid changes to the game, rather than what goes on around it, are also a major problem for tennis.
Why get 15 points when you win one?
Why is a shot from mid-court in basketball not 50 pts? Does it really matter? If people want to know why it's 15-love, then they can read up a little on the history of how it all started. It's not difficult.
You can ask many questions of many sports, tennis is no different.