If you look through the list you can see that most of the businesses are unlikely to be  offshoot "brands" for the sake of targeting bitcoin enthusiasts. I would expect many of these businesses to accept fiat in person, but the fact that their website only accepts bitcoin does somewhat limit the amount of fiat they take in. I am under no misapprehension that most of the btc gets turned into fiat and vice versa for all businesses. The point is there is a greater probability that a certain percentage of bitcoin stays within our ecosystem with these businesses and that is good enough at this stage. Just like how overstock keeps 10% in BTC (despite that a percentage   of it may eventually be turned into fiat when they offer to pay their employees bonuses in bitcoin.) This delay in leaking to fiat and or the fact that a certain percentage will keep some in bitcoin will help our ecosystem.

This discussion does bring up another business idea or opportunity. Create bitcoin only accepting businesses that hold profits in bitcoin (which can be proven and verified on the blockchain) for a certain set of time (1-5 years). It would have to be examples where it is a side business or hobby and the owner is in bitcoin for the long haul. Another concern for this idea is the tax implications of amassing such a store of bitcoin so may be better suited for businesses that are anonymous in nature and /or offer digital products and services.