It is incorrect to assume that a glued joint is stronger than a Quick-Step Uniclic mechanical joint. In fact, the actual strength of glued joints largely depends on how the planks were glued. Did you use the correct glue? Was the glue applied correctly? How much glue was used? Was the glue able to cure long enough at the correct temperature? Wasn't the floor walked on too soon after gluing, so that the joints were not able to cure properly?
The Uniclic joint, by contrast, is synonymous with a perfectly installed Laminate floor giving full satisfaction for many years. You can lay the floor by just clicking the planks together and without glue. The joints are guaranteed to stay together. Moreover, Uniclic offers many additional benefits: