Uh. In any complex application, you write services which are responsible for various business needs, and whose responsibilities only loosely overlap the way your webapp is accessed from the outside. You may even have services only used by other services.
And obviously, stuffing your business logic along with your web glue (whatever concrete representation you're sending to the outside, you're still stuffing parameters in a template, essentially) still violates SRP. Not to mention that it makes it utterly impossible to reuse outside of your web application, something which is sometimes desirable.
I don't disagree with you. In fact, I am writing those services whether it is for the API component or in the web glue on projects I worked on.
I'm just pointing out that there are a fraction of Rails crowd that don't think these services are needed is partly because of how things work in Rails.
And obviously, stuffing your business logic along with your web glue (whatever concrete representation you're sending to the outside, you're still stuffing parameters in a template, essentially) still violates SRP. Not to mention that it makes it utterly impossible to reuse outside of your web application, something which is sometimes desirable.