In 1993 Philips was looking at ways to give CD-i more visibility in shops. I like the fact that retail actually demanded Philips to switch to regular jewelcases otherwise they would not take CD-i in stock (or give it more exposure), as they had to buy specific shelves and trays that could hold the cd-i's. The position of CD-i was not that good so Philips decided to switch to regular jewelcases! This info came directly from Philips Media Games David McElhatten, so it's difficult not to believe it...
There might be several reasons why CD-i was not available in every games-shop or electronics store. One of them seriously was the need of a specific space to display the titles in. Every system demanded its own corner with its own promotional shelf. Several shops wanted to have a universal display with all the different boxes being displayed together. At one point, Philips wanted to be more visible in regular shops. As retail would not want to have CD-i in stock because of the jewelcase-size, Philips needed to switch to regular jewelcases in order to get a place in more stores. And they did, because the position of CD-i definately needed a boost!
[Thanks, David McElhatten]