Charity Greetings Cards - Why do they have to be just for Christmas??

Why is it that Charity Greeting Card packs are limited mostly to being released at only one time of year: Christmas..?? Wouldn't it be good to have occasions and blank packs, or Birthday Card packs people could buy for a variety of there favourite charities, during all times of the year?? I know that, occasionally, you can get them from catalogues and things, but not enough choices from as many places as they should be widely available from... Things like Recycling and Fair Trade/Shopping Locally for Locally sourced things could also be taken into account when creating such charity card packs... Promote more opportunities, and more responsible shopping, both to help humanity and animal welfare..!