During the night-club questchain you find out that there is a 2 mm large hole in reality in the gable of the church, that is slowly devouring the world around it. It is suggested, that it is the pale metastasizing like cancer into the isolas and not only surrounding them anymore. It is then assumed that the pale interferes with reality, leading to a zone of failure, consisting of the apartment building with the bookshop, the dicemaker and the whirling-in-rags. Joyce talks about how exposure to the pale leads to terrible experiences and forces you to relive memories and your past, which can't be conducive to trying to build a business.

The alternative explanation is simply that it is because of capitalism. Most business fail for one reason or the other and you only get to hear about the successful ones because of survivorship bias. Martinaise is a war-torn place and with very little wealth to go around, it's not extremely surprising to see businesses fail under these conditions. See also the game development studio, that wanted to create a Radio-wave MMO with like 4 people in a cellar. :::