That is not always the case. Lots of times I ended up re-implementing rails in Sinatra or so.

e.g. Rack -> Brochure -> Sinatra -> RailSinatra (half-ass Rails'ish Sinatra).

Things like crsf protection, email sending, asset pipeline etc. are not available/usable by default in small frameworks. It is good for learning to start with the simplest approach and build all the way up to the need as the project evolves, but it's bad if you have limited resources.

Successful projects tend to evolve and you can save lots of time by starting with a powerful framework. You just need to judge if the project has potential to grow, because the downsides of using a big powerful framework are not always that bad.