I don't know if it is an American VS European thing or just personality styles universal across all cultures. Been on here a short time as I am researching to set up my first tank and I have to say that 90% of the tanks posted are way over stocked in a produce section display that you would see at a grocery store. It is great if you are "trading pokemon cards" like you say, but are very unattractive to step back and take in as a whole. Getting up and close to look at every little detail i'm sure looks great, but there isn't much consideration given to the whole picture. That is not a bad thing, but some people are more visual than others and this hobby seems to predominantly attract scientific and analytic minds more than visual and creative minds. I am willing to bet a lot of it is collector mentality, but I think a lot of it might also be attributed to a few other things:
1. Rock supply used is mostly bulky in generic boulder shapes or in branching styles that are overly "branchy". It takes a lot more rock (cost), work and time time really break up what you got and put that puzzle together in an aesthetically pleasing way. Most people want to throw that rock in the tank and get on with it, cause after all you got into the hobby to get fish and or coral in a tank.. not be a sculptor.
2. It takes a long time to let a tank grow out with what would most likely be appropriate stocking for your tank to get to the point where it looks great. Impatience leads to overstocking.
I'm hoping I will overcome the impatience regarding stocking my tank, and have already butted heads with generic size/shaped rock selections limiting the creativity of sculpting 3d space.
Either way, enjoy what you like and if one style suits you, pay no mind to the stuff that doesn't!