It also depends on where their growth is from.. they got massive growth in China.. who can't really access youtube, spotify, etc.. As a couple of others have said, c-fans do buy outside of c-bars.
As for where I'm in (Canada), I know way more ppl who bought the album.. like 10x more. None of us are streamers. Also the lower cost of digipacks make almost no difference for us as the shipping costs more than the albums itself.
Perhaps they haven't grown a whole lot in the countries known for their streaming?