There's nothing confusing or surprising about the popularity of the surf candy, but I do often wonder why some other flies fail to get the same traction. It's pretty clear to me that fish catching isn't really the deciding factor in the popularity of patterns. The difficulty of tying can be a factor, but that doesn't really account for flies that people buy. Then there's durability, but I'm not convinced that lack of durability really puts people off that much either, up to a point. I guess this is also linked to target species, certain species I wan't to catch loads of fish on a single fly, but others, especially in saltwater, I might be happy with a single fish on a fly before it needs to be replaced.. trout vs trigger fish is what I'm thinking here. Obviously, sexiness is part of the equation. Flies for sale need some degree of bin appeal, It's not enough just to be a good fly.
The rubber candy is, I think, a great example of this. Like the surf candy, the rubber candy is one of Bob Popovic's creations and it is a great fly, but for some reason it just doesn't seem to be as popular. Perhaps it's because it's so similar in appearance to the surf candy, although its silicon body causes it to behave quite differently when fished. It has a wonderful slow floating/suspending action that the hard fly just can not replicate while still giving that slim minnow profile. Of course, it's a bit less durable than the surf candy, but it feels nice and soft which I'm convinced makes fish more likely to hold on to it or try to eat it multiple times if they don't get hooked first time. Admittedly silicon isn't as easy or pleasant to tie with as resins are, but other than that I can't really understand why it hasn't caught on as much as the surf candy.
If you haven't tried the rubber candy, go out and get yourself some silicon and give them a try, this fly really is an unsung hero that deserves more attention.