Ruby on Rails apps have started causing a lot of problems for a lot of people. Any small initial gains obtained by getting Ruby on Rails web apps put together and deployed rapidly have time and time again been lost many times over due to performance problems, severe maintenance headaches, security flaws, and other issues such as those.

In short, it hasn't managed to live up to the immense amount of hype that once surrounded it.

Those issues, combined with many other languages now offering web frameworks that are far better than Rails, have caused a lot of developers and organizations to completely abandon it and apps written using it. Few people and organizations have time and other resources to dedicate toward something that is a liability, especially when the alternatives are so plentiful and better these days.