Be that as it may. I don't buy from Kobo anymore unless I can't get the book anywhere else or there is a really great discount code that I can use on a book that allows me to use it. Unfortunately for Kobo (and myself) it is rare that these two coincide. Combine that with lack of a shopping cart, other places get my business as I usually buy upwards of 5 books at a go. Particularly if I run into a series or author I find I really like.
Personally I don't see why the two can't coincide. Add books to a shopping cart, go to check out when you are done, books that allow discount codes have a spot to enter a code (books that don't tell you so). Choose which book you wish to use whatever code you have on, enter code, site validates each code, click finish purchase, proceed to pay and you are done.
Ahh well just being too simplistic I guess. Since they haven't done that it must be too hard to implement.