Frame size is actually quite important for fitting a bike to a person. However, it's certainly something that could be varied within a model, just like a shoe has different sizes, or whatever. Multiple frame sizes are available on everything but the cheapest bikes - I had a choice of frame sizes on a standard Schwinn aluminum-framed bike 15 years ago.

Given the choice of 5 high-end bikes and the ability to select a proper size I don't really see a problem.