Problem is, any skill that isn't in the grails shop because it's a high demand expensive one like CC,DC also wouldn't be in a theoretical specific skill shop for the same reason they're not in the grails one.
They want people to spend money to get the good stuff.
With respect to that, it'd be good if they made said skills more available in the general pools. CC is only available on 2 seasonal units and 1 Gen 1 unit, 2 of which are in the colourless pool. DC has had at least a R/G/B unit since the mass purging happened (or will do, once Nagi drops), as well as 2 Legendary units, 2 seasonals and 1 Gen 1. You cannot pull a unit with Close Counter on new unit banners, and are at the whim of whoever IS stick on Legendary/Mythic banners if they decide to drop one on there, which is where people will tend to gravitate towards. Rerun banners have massively diluted odds for any 5* unit, and who would want to snipe colourless with Mist running around the 5* pool? If they want money, start making units with the skills people want more available.
There are other skills that are locked out in a similar fashion, by CC is the glaring issue given that DC has popped up so much AND so few prf weapons provide a CC effect compared to DC ones, even conditionally.