You're bike shedding [0].
Rails/DHH took already established design patterns and made strong opinions into a convention on the folder hierarchy of where you store your code. You can change that hierarchy, its not set in stone. It will require a lot of change. I've been on teams and it isn't just on-boarding time, its countless hours trying to find code written by someone no longer there that had their own layout of where files should go. Without conventions, people will run amok with a file structure. Multiply that by the number of developers on the team with attrition and different view points on organizing files and it can be a giant mess after a number of years. Its all a waste of time and has nothing to do with the quality of the code, what domain the application is in or anything really.
If you love Ruby there are other libraries out there like Sinatra [1] that don't have the conventions of Rails.