I think the allure is in the barriers to entry.
I see a lot of heavy lifters who start out solo, or lift in groups of 2 or maybe 3. They use their time efficiently and get a lot done, they don't spend the whole day in the gym and besides the casual chat with other people in the gym, they don't form a huge group. The heavy lifters do routines that seem impossible to start with. Nobody looks at a powerlifter and says 'sure, I'll do that'. You have to start small, and then good form is really important. Frankly it may even be a bit scary to step into the weight room and start with light weights, unsure of your form.
Then there's cross-fit. It's mostly done in huge groups by people of various levels of fitness. It's very vocal, it's very collective/team based. While exercises are done individually, they're done within a group, often with some form of coaching. Anyone can start, form isn't a priority and from what I've seen, form is adjusted to finish the exercise, meaning you can take shortcuts and use bigger weights and do more reps easier, without actually training as hard as when you'd have used 'proper' form.
It's inviting with low-barriers to entry.
The thing that surprises me is this, once you're doing cross-fit for a few months, get into it, do your reading on diet, resting and exercises, how the hell you can continue doing cross-fit is beyond me.
That having been said, a guy above this post said 'do whatever works for you'. And I really agree with that. Somehow some people really dig cross-fit and it's the only thing that gets them excited about exercise. If that's true, then great. I applaud cross fit for that reason alone. As long as they don't lift really heavy with bad form like I've seen some do, cause that can give you injuries you'll feel every day for the next 20 years. It's that bad.