I said this before, but i have come to these conclusions.
1.) BMX Is more dangerous. Most moms see kids on BMX bikes beating people up in movies, which makes them believe if a kid rides a bike he automatically does drugs and beats up kids. They see things that really look dangerous (that arent really that bad) like a 360 or a tailwhip and it is visually frightening to see a bike ridden in such a way. Skating is much less terrifying to see.
2.) Skating is dirt cheap, let's be honest. In comparison to BMX of course. a GOOD bike is at very least 400. A good board is maybe 100-200$. Unless you snap boards constantly you arent spending much at all.
3.) BMX Bikes are cumbersome to transport. You have to have an SUV/Hatchback/etc. to get a bike in without taking it apart or having to pull out racks for the back or roof. Moms/Dads dont wanna lug the bikes around when you can pop 50 skateboards into a Nissan Micro. haha
4.) BMX is hard. Scooting is easy, the basic skating really isnt as hard as BMX. You can learn to Ollie in a day when learning to bunny hop can take weeks. (this is on average, an ollie is easier than a Bunny Hop)
There are a lot more reasons but i really wish people saw what we saw. BMX is better, more fun (when done right), and safer i believe.
The thing is, BMX is not AS popular for just those reasons. The question is, why would you want BMX more popular?? Girls liking guys that did it? For it to be looked upon more fondly? It wont be, sadly. Not for a little while or until MTV makes a show about it (LOL). BMX comes in fads and things like that. You cant do anything about it. In the 80s, HUGE, in the 90s Mat Hoffman!!, in the early 2000s, dead!!, now, on the rise, i believe. It is on it's way to being popular in the USA. YOU have to help it, by setting a good example. We all do.
Personally, i have moved on from wanting it to be popular. I think if i ever make it to being a big rider i will do what i can to make it looked upon better, like Nigel Sylvester kind of. haha sadly, people are still racist so lots of people turn away right when they see the color of him.
References: OneGuyIlluminatiEye, robinson79, Brian Griffin, The Horror Contact, StoreBoughtChild, C_Johnsonbmx, dkTechEthan, etc.