If they are anything like the company I work for, only they are smaller, then what one department does, won't be known by others. Retail online sales, warehousing and marketing are separate departments that normally don't communicate with each other. the online department will have their list of all items sold, produce their web page to reflect all items, while Marketing targets certain groups with the latest and greatest. They take a gamble on products in the catalogs in the hopes that what is presented will be sellers. There is only so much they can fit in the catalog to make it viable for mailing. If they put everything in and make it like a phone book, the cost to ship outweighs any benefit they would obtain through catalog sales. Warehousing though, that is the fine line department. They have a lot of research to do in order to stock the best sellers and not stock items that rarely sell, after all, that is money sitting on a shelf collecting dust, taking up space that more profitable items can occupy.
Supply and demand. Get it right and you have a good profit margin, get it wrong and you can lock the doors.