Just to clarify I never said that someone who doesn't track their car isn't an enthusiast. It's just that in my experience, the people who track their cars are among the most enthusiastic owners that I've met. They have an understanding and relationship with their cars that can't be duplicated by just driving it on the street. If you truly enjoy driving your car, tracking your car adds an entirely other dimension to that enjoyment. Autocross doesn't count as tracking your car, but it will give you an understanding of the dynamics of your car that you just can't experience on the street. It seems there are some people who are awfully defensive about their decision not to autocross or track their car, claiming that driving their car on the street makes them just as much of an enthusiast. I disagree, because I believe that there are different levels of enthusiast. And I don't agree with the other analogy that was made about photography, it's just not really the same thing.
Also to clarify, tracking your car usually doesn't mean competition and I have never driven a car on the track in competition. Most non-professional enthusiasts who track their car attend a BMW CCA High Performance Driving Event which is not a competition. It is not timed and there is no contest. It is the opportunity to get your car on a track, usually with an instructor, and learn how to drive your car to the max. You learn about the proper line, turn-in, apex, and track-out points, and how to pass (always only by point by) in your own car. You learn about early apex, late apex, trail braking, left foot braking, heel-toe downshifting, and much more. Porsche Club of America (PCA) offer similar schools. In addition there are many other organizations that offer track sessions or "hot lapping". None of this involves timing or competition. There are also commercial driving schools; Skip Barber and Bob Bondurant racing schools are probably the most well known, but these are done with dedicated track cars. I took the Skip Barber 3-Day Racing School at Laguna Seca which is done in dedicated open-wheel race cars. Again, not a competition.
Those who want competition can choose from BMW or PCA club racing, or SCCA racing. This will be in your dedicated track car which has to meet stringent safety standards such as roll cages, fire extinguishers, fuel cells, nomex suites, balaclavas, and gloves, among many other requirements. This isn't just tracking your car, this is racing.
To make some proper analogies, and ones that are strictly car-related, most of us would agree that a Prius owner probably doesn't experience quite the same driving experience that we do in our BMWs, and most would agree that its a lesser experience. Someone who drives a 328i convertible, while still a BMW, is getting a different driving experience than someone who drives an M3. Someone who drives their car only on the street isn't getting nearly the same driving experience as someone who autocrosses their car. Tracking your car is another step beyond that. I'm just expanding on what captainaudio said.
But different strokes for different folks. Be content to drive your car on the street or push your limits a little and try an autocross. Go farther and take your car to the track. I would argue that doing either will make you even more enthusiastic than you are now. Everyone can make their own decisions how they define their enthusiasm for their car. IMHO, the true measure of an car enthusiast is how much they enjoy actually driving their car and hopefully, some of that would include driving it at the limit.