For me personally it's because Rails is so fucking slow these days. That's it, I don't mind having all that structure and ceremony sitting there. It doesn't stop me from architecting things however I please in lib/ and app/models/. But when it takes seconds for a brand new app to run `rake -T` it forces me to look for speedier alternatives. Speed will probably be what ultimately pushes me off Ruby as my bread and butter for good some day.