If you're in a pro shop, doing this kind of stuff a lot, I can see the use of a CAB. I am not and I have a CAB for plain sandpaper and one for Trizact (they use opposite parts of the velcro). and I've even stopped using them for the Trizact, mostly because I have to change the pads for different grits.
They're handy if you have one for each grit but at a minimum of $25 per and some places charge as much as $35 per CAB, that's way too expensive of an unnecessary accessory.
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"None are so blind as those who will not see."