When Marco Arment decided to make his podcasting app Overcast free and ask for donations instead, there was some pushback that it would destroy developer pricing. Actually I believe that it is a viable model for popular apps, but that it will have less impact on developer pricing than free-to-play games.
Patronage basically changes the motivation to pay from “I want to use the app, so I pay” to “I am feeling better when I support this app”. Patronage will normally deliver less revenues, as only some of the people with a money surplus will pay, but then often more than what the market price would be. It requires a large base of affluent users that could become patrons to generate a good amount of revenue. So it is a viable business model for apps that deliver good value to a lot of customers. It essentially leaves a lot of money in the table, and when the value delivered is much greater than the cost to provide it, it suffices to have a small percentage of users supporting the development.
As could be already seen in the popularity of Pocket and Instapaper, such markets delivering huge surpluses are an attractive target for Venture Capital. VCs want to make money, so they attempt to corner the entire market so that they can extract money from ancillary services thanks to their market position. This is also why the influence on other software markets is more limited: Patronage only works in markets that are also attractive targets for VC founded companies, and is in my eyes vastly preferable to having a market dominated by a rent extracting startup. I simply trust the users to do better with their saved money than what a rentier would do with his surplus.