Because that " Show Lore" button doesn't exist in a vacuum. They were asked directly about whether or not there are grimoire cards in Destiny 2 and they said "no" twice. They didn't say " Yes, but now we are calling them Y instead and they are in game", and they didn't say " No, but we have something similar". They instead listed off other in game lore sources they would focus on, none of which fill the niche of grimoire cards. Existence is inherently ambiguous. For all I know existence is a simulation and every one is a philosophical zombie except for me, parsimony is really the only hope anyone has in making sense of the world. Parsimoniously, given what we know, and what we don't know, and given what has been said, and what they didn't say when given the opportunity, the logical conclusion to draw right now, if any, is that there is no grimoire equivalent story telling in Destiny 2 as of May 2017. Respectfully voicing criticism of this decision is the best way to get them to pivot if we are right, and we are probably right.