I also tend to think that planted aquariums will never be anywhere near mainstream because of the already mentioned reasons: it often takes a great deal of time, knowledge, effort, commitment, $$, etc. How can that compare to sitting on the couch and watching Comedy Central?
Bonsai has been around for a long time. A large chunk of people can recognize a bonsai tree even if it's just from Karate Kid. Yet, who keeps Bonsai? No one around me, that's for sure. No one is willing to learn about the techniques or invest the decades that Bonsai requires.
Some hobbies will always be limited to specific personality types, no matter if every Walmart is full of the supplies and books and displays because some hobbies require time and work and that will always put off the great majority of people.
Thank goodness. Things go to hell when they go mainstream because they get taken out of the hands of the people that actually care.
"Insanity: doing [or asking] the same thing over and over again and expecting different results."