This also makes me think of the problem of legacy code. Once you've written an app, it's feature complete, and it's profitable, expending effort to rewrite it in a new tech is not only a questionable value proposition, it can be actively dangerous. Replacing ugly but works with beautiful but fails is not good engineering.
Plus, if you're going with some trendy new framework that emerged in the last month, chances are that when you do need maintenance, no-one'll be around who wants to work on it.
