Because there's absolutely no narrative purpose for it other than to satisfy people who want the characters to more accurately reflect common D&D player strategies, and I am actively seeking to disappoint such people so they stop expecting that. Basically, the fact that "every decent player" does something has become a reason for me to NOT do it now, just to try to get people to stop asking.

Given that I've never listed what spells V has, what possible difference would it make for him/her to cast some of them from memory and some of them from a staff, other than making more work for me to have to explain to the readers, "This spell came from the staff!"?

Also, because it would be a pain in the ass to have to keep track of one more large equipment object in every panel V appears in. Is he/she holding it? Where did he/she leave it? Which hand was he/she holding it in last panel? Malack's staff has turned into an annoyance in that regard, hence the reason he put it down right before the fight began. I'm not about to make things harder for myself for no benefit.