Not everyone is rolling every SSR Kamihime Gatcha, or getting the kamihime needed when they do. Not everyone is devoting equal effort to every grid. Not everyone even cares about being able to complete these challenges.
In my case, all 3 apply. I often don't attempt the challenges even when I think I can clear them. A handful of raid tickets isn't worth my time tediously shuffling through the menus swapping in characters and equipment and then swapping them out again afterwards. Not when I can mindlessly hit the quotas (guaranteed) for an MLB weapon and eidolon just by spamming battles with a pre-set team for 3 or so Burst hours. *shrug*