We had this problem at work: a Sinatra app that had pieces and pieces of ActiveSupport bolted on, and it got to the stage where we needed a beefier database than Redis before the CTO eventually generated a new rails app and transplanted the Sinatra app on top of it.

It's all well and good saying "use Sinatra", but when you get to the stage where you're adding ActiveRecord because it's the most mature ORM out there, it's usually late enough in the game that you're actually writing a poor excuse for a Rails application.

My point is - some of us are trying to build websites and get work done and were attracted to a full-stack framework so we didn't have to keep reinventing the wheel and so we can benefit from an ecosystem.