Initially I couldn't have answered the question posited here, but having hunted around the web I think I can categorically state that the reason I got into and make card models is simple. I absolutely cannot get the majority of the models I've collected anywhere. This is partly because I live in a country where the larger population do nothing outside of watching soap opera and reality shows and partly because I live on a rock where there are virtually no stores which stock anything worth having. Also, partly because some of the things I've got simply are not made in any other medium.
My particular fields of interest lie in submarines, sailing/steam ships, starships and mechs (at the risk of heresy not Gundam or Robotech). The only submarine I've found that was worth having was a 1/72nd scale from Revell, but in card models I've found several including two beautiful u-boats from UHU and Thai Modelling (still yet to order that one.) Sailing vessels are notoriously expensive if one wants something decent, and thus far the only way I've been able to get anything at the scale I like is via Partworks magazines. Of course, card modelling companies make dozens of sailing vessels, steam and warships. Heaven...
Mechs though, I've not found a supplier in the UK that doesn't ask a fortune for import from Japan, but with card there are loads and no import costs.
All in all, cost wise, card modelling is cheaper. Even the price of the commercial models is less than I would pay for other materials. A win-win situation. It is just as satisfying cutting and constructing a card model as it is any other model, and while there may be a few small issues regarding robustness, it's not serious enough to cause concern.
Also the creativity and industriousness of those who contribute their time, skills and bandwidth is awesome. How can one not respect people who make such supreme efforts to make things that they like, and then offer then free of charge to others so they can enjoy making the models as well.
Simply amazing.
Even my wife has no complaints (other than the growing collection of models)... It keeps me quiet and out of mischief, doesn't cost a new mortgage and produces some fine looking models.
What's not to like?
