I suspect a good ecommerce module is larger and more complex than EE and all of it’s modules combined. Not to mention the documentation and homework Ellis Lab has to do in order to support the product.
Stephen is correct here. It has been a truly immense project, particularly given the tiny size of our dev team, which not only must advance EE itself but squash bugs and help with support. If I could magically make a commerce system appear I would. It’s been the single most requested item, and one that I believe will be very successful for us.
A commerce system, when you consider everything it needs to do, from shipping, to collecting tax (the state of New York alone has a couple hundred different tax rates), to discounts, to coupons, to financial reporting, to integration with all the different credit card processing gateways, to management of products, to security, etc., is really a large software application in its own right. It will likely eclipse the size of all our other modules combined.
People sometimes think we’re a big company because we have a nice site and a large community, but we’re actually a pretty small team. Until a couple years ago it was basically Paul and I, so we are growing, fortunately, which means our development is getting faster. The bottom line is we’re doing the best we can, and as another person mentioned, we really do care about our product and our community, and we do try to make decisions that are in the best interest of everyone.