It lacks expressiveness, which means you actually have to put some thought into your design to avoid butting heads with it. You can't throw up garbage and then keep massaging the types until you can make whatever gobbledygook you came up with fit.

Business/safety critical logic tends to get complicated, and, at least in the case of business software, is more than likely is venturing into unexplored territory, so when you're not very skilled at programming finding the right design can become an insurmountable challenge. A more expressive type system offers a bandaid to work around that.